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1.
Structural view of cadherin-mediated cell-cell adhesion 总被引:1,自引:0,他引:1
Following the multiplication of biochemical, biophysical and structural studies describing cadherin molecules and their interactions,
several ideas have emerged to explain the mechanisms of cadherin-mediated cell adhesion. Although different models were proposed
for cadherin interactions, a consensus has come forth considering lateral dimerization of cadherins as being a central component
of the cell-cell adhesion process. This review summarizes the recent development in structural studies of cadherins.
Received 14 September 1998; received after revision 14 November 1998; accepted 16 November 1998 相似文献
2.
Structure, function and evolution of antifreeze proteins 总被引:16,自引:0,他引:16
Antifreeze proteins bind to ice crystals and modify their growth. These proteins show great diversity in structure, and they
have been found in a variety of organisms. The ice-binding mechanisms of antifreeze proteins are not completely understood.
Recent findings on the evolution of antifreeze proteins and on their structures and mechanisms of action have provided new
understanding of these proteins in different contexts. The purpose of this review is to present the developments in contrasting
research areas and unite them in order to gain further insight into the structure and function of the antifreeze proteins.
Received 2 September 1998; received after revision 21 October 1998; accepted 2 November 1998 相似文献
3.
Much effort has been devoted recently to expanding the amino acid repertoire in protein biosynthesis in vivo. From such experimental
work it has emerged that some of the non-canonical amino acids are accepted by the cellular translational machinery while
others are not, i.e. we have learned that some determinants must exist and that they can even be anticipated. Here, we propose
a conceptual framework by which it should be possible to assess deeper levels of the structure of the genetic code, and based
on this experiment to understand its evolution and establishment. First, we propose a standardised repertoire of 20 amino
acids as a basic set of conserved building blocks in protein biosynthesis in living cells to be the main criteria for genetic
code structure and evolutionary considerations. Second, based on such argumentation, we postulate the structure and evolution
of the genetic code in the form of three general statements: (i) the nature of the genetic code is deterministic; (ii) the
genetic code is conserved and universal; (iii) the genetic code is the oldest known level of complexity in the evolution of
living organisms that is accessible to our direct observation and experimental manipulations. Such statements are discussed
as our working hypotheses that are experimentally tested by recent findings in the field of expanded amino acid repertoire
in vivo.
Received 30 June 1999; accepted 9 July 1999 相似文献
4.
Visual pigment: G-protein-coupled receptor for light signals 总被引:5,自引:0,他引:5
The visual pigment present in photoreceptor cells is a prototypical G-protein-coupled receptor (GPCR) that receives a light
signal from the outer environment using a light-absorbing chromophore, 11-cis-retinal. Through cis-trans isomerization of the chromophore, light energy is transduced into chemical free energy, which
is in turn utilized for conformational changes in the protein to activate the retinal G-protein. In combination with site-directed
mutagenesis, various spectroscopic and biochemical studies identified functional residues responsible for chromophore binding,
color regulation, intramolecular signal transduction and G-protein coupling. Extensive studies reveal that these residues
are localized into specific domains of visual pigments, suggesting a highly manipulated molecular architecture in visual pigments.
In addition to the recent findings on dysfunctional mutations in patients with retinitis pigmentosa or congenital night blindness,
the mechanism of intramolecular signal transduction in visual pigments and their evolutionary relationship are discussed.
Received 20 July 1998; received after revision 9 September 1998; accepted 23 September 1998 相似文献
5.
C. Elsing J. Górski C. Boeker W. Stremmel 《Cellular and molecular life sciences : CMLS》1998,54(7):744-750
Studies of regulation of free fatty acid (FFA) utilization by skeletal muscles have focused on plasma FFA delivery and on
intracellular factors affecting FFA metabolism. The present study was conducted to directly analyse the uptake process of
fatty acids into single myocytes. Cells were isolated from the rat flexor digitorum brevis muscle. Confocal laser scanning
microscopy was utilized to analyse the uptake of the fluorescent fatty acid derivative 12-NBD-stearate, which is not metabolized
by muscle tissue. Uptake represented a saturable function of the unbound fatty acid concentration in the medium (K
m 366 ± 118 nM, V
max 2.1 ± 0.3 AU/s) and depended on the medium sodium concentration. Reduced buffer pH increased initial uptake rates, whereas
lactate (10 mM) had no effect. Membrane hyper- and depolarization decreased uptake rates. This study demonstrates for the
first time kinetic data from isolated myocytes with evidence for a carrier-mediated transport mechanism for long-chain fatty
acids.
Received 31 March 1998; accepted 8 May 1998 相似文献
6.
M. P. Mollica S. Iossa G. Liverini S. Soboll 《Cellular and molecular life sciences : CMLS》1998,54(11):1277-1282
Changes in mitochondrial function were studied in perfused liver from rats aged 24 – 365 days. Oxygen consumption together
with the rates of gluconeogenesis, urea synthesis and ketogenesis were determined. Basal mitochondrial respiration as well
as the ability of the liver to synthesize glucose, urea and ketone bodies declined from 24- to 365-day-old rats. On the other
hand, on transition from 24 to 60 days the liver oxidation rate of hexanoate, sorbitol and glycerol is enhanced, but not of
ketone bodies or palmitate. Our results show that the transition from weaning to middle age is accompanied by defined changes
in hepatic substrate oxidation. From the observed time course of the decrease in basal and substrate-stimulated oxygen consumption,
it is concluded that in rat liver cells a decline in respiratory chain function, long-chain fatty acid and ketone body metabolism,
gluconeogenesis and ureogenesis occurs at a relatively early life stage.
Received 19 June 1998; received after revision 11 September 1998; accepted 11 September 1998 相似文献
7.
The structure and function of heterotrimeric G protein subunits is known in considerable detail. Upon stimulation of a heptahelical
receptor by the appropriate agonists, the cognate G proteins undergo a cycle of activation and deactivation; the α-subunits and the βγ-dimers interact sequentially with several reaction partners (receptor, guanine nucleotides and effectors as well as regulatory
proteins) by exposing appropriate binding sites. For most of these domains, low molecular weight ligands have been identified
that either activate or inhibit signal transduction. These ligands include short peptides derived from receptors, G protein
subunits and effectors, mastoparan and related insect venoms, modified guanine nucleotides, suramin analogues and amphiphilic
cations. Because compounds that act on G proteins may be endowed with new forms of selectivity, we propose that G protein
subunits may therefore be considered as potential drug targets.
Received 18 September 1998; received after revision 6 November 1998; accepted 11 November 1998 相似文献
8.
Scavenger receptor family proteins: roles for atherosclerosis, host defence and disorders of the central nervous system 总被引:11,自引:1,他引:10
Y. Yamada T. Doi T. Hamakubo T. Kodama 《Cellular and molecular life sciences : CMLS》1998,54(7):628-640
In this review, we summarize the structure and function of the scavenger receptor family of proteins including class A (type
I and II macrophage scavenger receptors, MARCO), class B (CD36, scavenger receptor class BI), mucinlike (CD68/macrosialin,
dSR-CI) and endothelial (LOX-1) receptors. Two motifs have been identified as ligand-binding domains a charged collagen structure
of type I and II receptors, and an immunodominant domain of CD36. These structures can recognize a wide range of negatively
charged macromolecules, including oxidized low-density lipoproteins, damaged or apoptotic cells, and pathogenic microorganisms.
After binding, these ligands can be either internalized by endocytosis or phagocytosis, or remain at the cell surface and
mediate adhesion or lipid transfer through caveolae. Under physiological conditions, scavenger receptors serve to scavenge
or clean up cellular debris and other related materials, and they play a role in host defence. In pathological states, they
mediate the recruitment, activation and transformation of macrophages and other cells which may be related to the development
of atherosclerosis and to disorders caused by the accumulation of denatured materials, such as Alzheimer's disease.
Received 17 September 1997; received after revision 16 March 1998; accepted 17 March 1998 相似文献
9.
Gineitis A Treigyte G Savickiene J Shanbhag VP Stigbrand T 《Cellular and molecular life sciences : CMLS》1999,55(2):317-326
The two-dimensional electrophoretic patterns of nuclear proteins and their tyrosine phosphorylation were compared for HL-60
cells before and after differentiation induction to granulocytes by dimethyl sulfoxide, all-trans retinoic acid and N
6,O
2-dibutyryl adenosine 3′5′-cyclic monophosphate. Regardless of the inducer used, some nuclear proteins, which are tyrosine-phosphorylated
in proliferating HL-60 cells, undergo gradual dephosphorylation 12–72 h after induction of differentiation, followed by drastic
dephosphorylation during maturation to granulocytes. At least 13 nuclear proteins with a molecular mass of 35–110 kDa are
dephosphorylated, and 6 nuclear proteins undergo tyrosine phosphorylation. Analysis of the nuclear proteins differentially
extracted by salt and detergents indicates that changes in their tyrosine phosphorylation during the maturation stage of differentiating
granulocytes occur mainly in proteins which are abundant in nucleoplasm, chromatin and residual nuclear structures. The abundance
of these proteins, residing in the nuclear structures, and their long-term modification in phosphorylation during the maturation
stages of differentiation strongly suggest that tyrosine phosphorylation of these proteins is involved in reorganization of
the differentiating cell nucleus.
Received 21 September 1998; received after revision 24 November 1998; accepted 3 December 1998 相似文献
10.
Platelet-activating factor acetylhydrolases (PAF-AHs, EC 3.1.1.47) constitute a unique and biologically important family
of phospholipase A2s. They are related to neither the well-characterized secretory nor cytosolic PLA2s, and unlike them do not require Ca2+ for catalytic activity. The distinguishing property of PAF-AHs is their unique substrate specificity they act on the phospholipid
platelet-activating factor (PAF), and in some cases on proinflammatory polar phospholipids, from which they remove a short
acyl moiety – acetyl in the case of PAF – located at the sn-2 position. Because PAF is found both in the plasma and in the cytosol of many tissues, PAF-acetylhydrolases are equally widely
distributed in an animal organism. Recent crystallographic studies shed new light on the complex structure-function relationships
in PAF-AHs.
Received 15 September 1997; received after revision 23 February 1998; accepted 25 February 1998 相似文献
11.
D. Robinette S. Wada T. Arroll M. G. Levy W. L. Miller E. J. Noga 《Cellular and molecular life sciences : CMLS》1998,54(5):467-475
Three antibacterial proteins were isolated from acid extracts of channel catfish (Ictalurus punctatus) skin by cation exchange chromatography and reverse-phase high-pressure liquid chromatography. The molecular masses of the
proteins were 15.5, 15.5 and 30 kD as determined by SDS-polyacrylamide gel electrophoresis. Mass spectrometry, amino acid
composition and amino acid sequence data suggest that the most abundant protein is closely related to histone H2B. The H2B-like
protein was inhibitory to Aeromonas hydrophila and Saprolegnia spp., which are important bacterial and fungal pathogens of fish. These findings suggest that histones may be important defensive
molecules in fish.
Received 22 December 1997; received after revision 5 March 1998; accepted 5 March 1998 相似文献
12.
H. Mueller 《Cellular and molecular life sciences : CMLS》1998,54(12):1291-1298
The discovery and cloning of the cytokine tumor necrosis factor α (TNF) gave rise to new hopes for a significant victory in the war against cancer. Preclinical in vitro studies in cell cultures
and in vivo studies in animal models demonstrated the antitumor capacities of TNF. Although clinical studies were largely
made possible by the availability of recombinant TNF, phase I and II clinical trials showed very quickly that the systemic
administration of TNF induced severe side effects mainly due to its pleiotropic action on immunocompetent cells. The clinical
manifestations of the side effects were similar to those observed during a severe infection and inflammation. Very recently,
lessons from these clinical studies yielded refined approaches whereby the toxicity of TNF is limited through local administration,
a combination with other therapeutic regimens and targeted gene therapy. These new approaches are slated for larger clinical
trials and in the near future might demonstrate the limited but powerful usefulness of TNF as an antineoplastic agent for
different types of cancer.
Received 7 September 1998; received after revision 15 October 1998; accepted 15 October 1998 相似文献
13.
At the end of mitosis, daughter cells are separated from each other by cytokinesis. This process involves equal partitioning
and segregation of cytoplasm between the two cells. Despite years of study, the mechanism driving cytokinesis in animal cells
is not fully understood. Actin and myosin are major components of the contractile ring, the structure at the equator between
the dividing cells that provides the force necessary to constrict the cytoplasm. Despite this, there are also tantalizing
results suggesting that cytokinesis can occur in the absence of myosin. It is unclear what the roles are of the few other
contractile ring components identified to date. While it has been difficult to identify important proteins involved in cytokinesis,
it has been even more challenging to pinpoint the regulatory mechanisms that govern this vital process. Cytokinesis must be
precisely controlled both spatially and temporally; potential regulators of these parameters are just beginning to be identified.
This review discusses the recent progress in our understanding of cytokinesis in animal cells and the mechanisms that may
regulate it.
Received 24 August 1998; received after revision 9 October 1998; accepted 9 October 1998 相似文献
14.
J. W. M. Lagerberg J. VanSteveninck T. M. A. R. Dubbelman 《Cellular and molecular life sciences : CMLS》1997,53(3):257-262
The fluorescent dye Merocyanine 540 (MC540) is often used as a probe to monitor the molecular packing of phospholipids in
the outer leaflet of biomembranes. In a previous study we showed that the increased staining of erythrocytes with a perturbed
membrane structure was mainly due to an increase in the fluorescence yield of cell-bound MC540, rather than to an increase
of the number of bound molecules. Erythrocytes and ghosts exposed to continuous fluxes of H2O2 exhibited pronounced lipid peroxidation. Further, red blood cells subjected to this form of oxidative stress also showed
increased staining with MC540. It appeared that this was caused by a strong increase in binding of MC540, together with a
slight red shift of the fluorescence emission maximum and a small increase in the fluorescence yield of bound MC540. The changed
MC540 binding characteristics were not observed when lipid peroxidation was suppressed by the presence of the antioxidant
BHT in the incubation medium. However, open ghosts exposed to H2O2 showed no increase of MC540 binding, excluding a direct involvement of lipid peroxidation. Measurement of fluorescence emission
spectra and gel filtration studies showed that MC540 can bind to H2O2-exposed hemoglobin. Experiments with erythrocytes lysed in hypotonic medium after exposure to H2O2 revealed that peroxidation of lipids with H2O2 induced a non-specific permeabilization of the plasma membrane to MC540, thereby allowing MC540 to bind to the oxidatively
denatured, more hydrophobic hemoglobin. These results indicate that conclusions about packing of phospholipids in the outer
leaflet of the membrane based on increased MC540-staining should be drawn with care.
Received 27 September 1996; received after revision 5 November 1996; accepted 27 November 1996 相似文献
15.
CD100 is a leukocyte semaphorin 总被引:5,自引:0,他引:5
S. Delaire A. Elhabazi A. Bensussan L. Boumsell 《Cellular and molecular life sciences : CMLS》1998,54(11):1265-1276
CD100 was originally described as an activation molecule on the surface of human T lymphocytes. Its triggering through distinct
epitopes leads to different signals of costimulation with phorbol myristate acetate (PMA) or with CD3 and CD2. Interestingly,
CD100 was shown to associate with different partner molecules in T cells. First, CD100 can associate with CD45, a key molecule
with protein tyrosine phosphatase activity involved in T-cell transduction this association is physical and has functional
consequences for both partners. Second, CD100 interacts in its cytoplasmic domain with a Ser/Thr kinase for which it represents
a preferential substrate. Recently, CD100 was identified as a member of the semaphorin gene family. This family comprises
approximately 20 structurally related proteins. The first semaphorins were identified in the developing nervous system. Function
has been shown for only some of them and involves repulsion during growth cone guidance. Since CD100 was the first semaphorin
identified in the immune system, this raises the possibility of the involvement of members of the semaphorin family in other
physiological phenomena outside the nervous system.
Received 1 March 1998; received after revision 8 June 1998; accepted 8 June 1998 相似文献
16.
K. Sandman S. L. Pereira J. N. Reeve 《Cellular and molecular life sciences : CMLS》1998,54(12):1350-1364
17.
Kirkpatrick DT 《Cellular and molecular life sciences : CMLS》1999,55(3):437-449
Numerous proteins are involved in the nucleotide excision repair (NER) and DNA mismatch repair (MMR) pathways. The function
and specificity of these proteins during the mitotic cell cycle has been actively investigated, in large part due to the involvement
of these systems in human diseases. In contrast, comparatively little is known about their functioning during meiosis. At
least three repair pathways operate during meiosis in the yeast Saccharomyces cerevisiae to repair mismatches that occur as a consequence of heteroduplex formation in recombination. The first pathway is similar
to the one acting during postreplicative mismatch repair in mitotically dividing cells, while two pathways are responsible
for the repair of large loops during meiosis, using proteins from MMR and NER systems. Some MMR proteins also help prevent
recombination between diverged sequences during meiosis, and act late in recombination to affect the resolution of crossovers.
This review will discuss the current status of DNA mismatch repair and nucleotide excision repair proteins during meiosis,
especially in the yeast S. cerevisiae.
Received 21 September 1998; received after revision 23 November 1998; accepted 23 November 1998 相似文献
18.
Regulation of caldesmon activity by Cdc2 kinase plays an important role in maintaining membrane cortex integrity during cell division 总被引:1,自引:0,他引:1
Li Y Wessels D Wang T Lin JL Soll DR Lin JJ 《Cellular and molecular life sciences : CMLS》2003,60(1):198-211
To study the mitosis-specific phosphorylation of caldesmon (CaD), we generated a mutant of the C-terminal fragment (amino
acids 244–538) of human fibroblast CaD (CaD39-6F), as well as a mutant of the full-length CaD (CaD-6F), in which all six potential
phosphorylation sites for Cdc2 kinase were abolished. The mitotic CaD39-6F-overexpressing cells required more time to progress
from anaphase start to 50% cytokinesis, exhibited larger size, and abnormally formed numerous small blebs. In contrast, overexpression
of the wild-type C-terminal fragment of CaD (CaD39) did not result in abnormal bleb formation, but led to larger size and
prolonged the time requirement between anaphase start and 50% cytokinesis. Similar abnormal blebs were also observed in the
CaD-6F-overexpressing cells. CaD-6F-overexpressing cells did not show larger size but required more time to progress from
anaphase start to 50% cytokinesis. These results suggest that mitosis-specific phosphorylation of CaD plays a role in inhibiting
bleb formation and that the N-terminal fragment of CaD is required for cell size determination.
Received 4 September 2002; received after revision 25 November 2002; accepted 4 December 2002 相似文献
19.
Bile acids and bile alcohols in the form of their conjugates are amphipathic end products of cholesterol metabolism with multiple physiological functions. The great variety of bile acids and bile alcohols that are present in vertebrates are tabulated. Bile salts have an enterohepatic circulation resulting from efficient vectorial transport of bile salts through the hepatocyte and the ileal enterocyte; such transport leads to the accumulation of a pool of bile salts that cycles between the liver and intestine. Bile salt anions promote lipid absorption, enhance tryptic cleavage of dietary proteins, and have antimicrobial effects. Bile salts are signaling molecules, activating nuclear receptors in the hepatocyte and ileal enterocyte, as well as an increasing number of G-protein coupled receptors. Bile acids are used therapeutically to correct deficiency states, to decrease the cholesterol saturation of bile, or to decrease the cytotoxicity of retained bile acids in cholestatic liver disease. 相似文献
20.
Stomatal guard cell responses to kinetin and natriuretic peptides are cGMP-dependent 总被引:3,自引:0,他引:3
M. Pharmawati T. Billington C. A. Gehring 《Cellular and molecular life sciences : CMLS》1998,54(3):272-276
Immunological evidence suggests that plants contain natriuretic peptides (NPs) and furthermore (3- [125I]iodotyrosol28) rat atrial NP (rANP) binds specifically to plant membranes. rANP and immunoaffinity-purified plant NP analogues also promote
concentration-dependent stomatal opening. Here we report that kinetin, a synthetic cytokinin, and rANP induce stomatal opening
in Tradescantia albiflora and that the effect of rANP is critically dependent on the secondary structure of the peptide hormone. The native circular
molecule is active, whereas the linearized molecule shows no biological activity. Furthermore, kinetin- and rANP-induced stomatal
opening is reversibly inhibited by two in hibitors of guanylate cyclase, LY 83583 and methylene blue. Stomatal opening is
also induced in a concentration-dependent manner by the cell-permeant cyclic guanosine-3′,5′-monophosphate (cGMP) analogue
8-Br-cGMP, and this effect is prevented by the stomatal closure promoting plant hormone abscisic acid (ABA). We conclude that
in guard cells kinetin and rANP pathways operate via guanylate cyclase upregulation, and we propose that ABA-induced closure
is not cGMP-dependent.
Received 1 October 1997; received after revision 2 December 1997; accepted 6 January 1998 相似文献