Hereditary spherocytosis associated with deletion of human erythrocyte ankyrin gene on chromosome 8

Hereditary spherocytosis (HS) is one of the most common hereditary haemolytic anaemias. HS red cells from both autosound dominant and recessive variants are spectrin-deficient, which correlates with the severity of the disease. Some patients with recessive HS have a mutation in the spectrin alpha-2 domain (S.L.M. et al., unpublished observations), and a few dominant HS patients have an unstable beta-spectrin that is easily oxidized, which damages the protein 4.1 binding site and weakens spectrin-actin interactions. In most patients, however, the cause of spectrin deficiency is unknown. The alpha- and beta-spectrin loci are on chromosomes 1 and 14 respectively. The only other genetic locus for HS is SPH2, on the short arm of chromosome 8 (8p11). This does not correspond to any of the known loci of genes for red cell membrane proteins including protein 4.1 (1p36.2-p34), the anion exchange protein (AE1, band 3; 17q21-qter), glycophorin C (2q14-q21), and beta-actin (7pter-q22). Human erythrocyte ankyrin, which links beta-spectrin to the anion exchange protein, has recently been cloned. We now show that the ankyrin gene maps to chromosome 8p11.2, and that one copy is missing from DNA of two unrelated children with severe HS and heterozygous deletions of chromosome 8 (del(8)(p11-p21.1)). Affected red cells are also ankyrin-deficient. The data suggest that defects or deficiency or ankyrin are responsible for HS at the SPH2 locus.     

Sequence of a Drosophila segmentation gene: protein structure homology with DNA-binding proteins

Mutations in the fushi tarazu (ftz) locus of Drosophila result in embryos with half the usual number of body segments. The sequences of the wild-type gene, a temperature-sensitive allele and a dominant mutant allele are presented. A portion of the conserved protein domain present in ftz and several homoeotic genes resembles the DNA-binding region of prokaryotic DNA-binding proteins, and is also similar to products of the yeast mating-type locus.     

Immunoreactive forms of human erythrocyte ankyrin are present in diverse cells and tissues.

Ankyrin is a polypeptide of molecular weight (MW) 200,000 which is tightly bound to the cytoplasmic surface of the human erythrocyte membrane and has been identified as the high-affinity membrane attachment protein for spectrin. This protein has also been shown to be associated with band 3 (ref. 4), the major transmembrane protein which links a cytoplasmic structural protein to an integral membrane protein. A water-soluble, 72,000-MW, proteolytic fragment of ankyrin has been purified which retains the ability to bind to spectrin, and competitively inhibits reassociation of spectrin with membranes. Monospecific antibodies directed against this fragment have been prepared and demonstrated to cross-react only with ankyrin among the erythrocyte membrane proteins. The present study reports the use of these antibodies to develop a radioimmunoassay capable of detecting femtomolar quantities of ankyrin, and demonstrates the presence of small but significant amounts of immunoreactivity in a variety of types of cells and tissues.     

A human T cell-specific cDNA clone encodes a protein having extensive homology to immunoglobulin chains

We have cloned and sequenced a human mRNA specific for mammalian T-lymphoid cells. The message was found to be expressed in human and murine T lymphoblasts, thymocytes and phytohaemagglutinin-stimulated T lymphocytes. The protein deduced from the cDNA sequence has a molecular weight of 34,938 and shows extensive similarity to the entire length of the variable, joining and constant regions of mammalian immunoglobulin light chains. In addition, the relative positions of the cysteine residues are similar to those of the light chains of murine and human immunoglobulin molecules. These properties suggest that the cDNA clone may correspond to a message that specifies part of the human T-cell receptor.     

Primary structure and expression of a functional human glucocorticoid receptor cDNA

Identification of complementary DNAs encoding the human glucocorticoid receptor predicts two protein forms, of 777 (alpha) and 742 (beta) amino acids, which differ at their carboxy termini. The proteins contain a cysteine/lysine/arginine-rich region which may define the DNA-binding domain. Pure radiolabelled glucocorticoid receptor, synthesized in vitro, is immunoreactive and possesses intrinsic steroid-binding activity characteristic of the native glucocorticoid receptor.     

Cloning of the gene and cDNA for mammalian beta-adrenergic receptor and homology with rhodopsin

The adenylate cyclase system, which consists of a catalytic moiety and regulatory guanine nucleotide-binding proteins, provides the effector mechanism for the intracellular actions of many hormones and drugs. The tissue specificity of the system is determined by the particular receptors that a cell expresses. Of the many receptors known to modulate adenylate cyclase activity, the best characterized and one of the most pharmacologically important is the beta-adrenergic receptor (beta AR). The pharmacologically distinguishable subtypes of the beta-adrenergic receptor, beta 1 and beta 2 receptors, stimulate adenylate cyclase on binding specific catecholamines. Recently, the avian erythrocyte beta 1, the amphibian erythrocyte beta 2 and the mammalian lung beta 2 receptors have been purified to homogeneity and demonstrated to retain binding activity in detergent-solubilized form. Moreover, the beta-adrenergic receptor has been reconstituted with the other components of the adenylate cyclase system in vitro, thus making this hormone receptor particularly attractive for studies of the mechanism of receptor action. This situation is in contrast to that for the receptors for growth factors and insulin, where the primary biochemical effectors of receptor action are unknown. Here, we report the cloning of the gene and cDNA for the mammalian beta 2AR. Analysis of the amino-acid sequence predicted for the beta AR indicates significant amino-acid homology with bovine rhodopsin and suggests that, like rhodopsin, beta AR possesses multiple membrane-spanning regions.     

In vitro formation of a complex between cytoskeletal proteins of the human erythrocyte.

The formation of a high-molecular weight complex between spectrin and F-actin depends on the presence of a third cytoskeletal constituent, protein 4.1. Electron microscopy shows that in this ternary complex the actin filaments are linked by bridges, which have the appearance of spectrin. The spectrin must be in the tetrameric state for such bridges to form: the dimer is evidently univalent, for it binds but forms no cross-links. G-actin also fails to form extended complexes. It is inferred that in the native cytoskeleton the spectrin is tetrameric and associated with 4.1 and probably oligomers of actin.     

Refined crystal structure of beta-lactamase from Citrobacter freundii indicates a mechanism for beta-lactam hydrolysis

Beta-Lactamases (EC 3.5.2.6, 'penicillinases') are a family of enzymes that protect bacteria against the lethal effects of cell-wall synthesis of penicillins, cephalosporins and related antibiotic agents, by hydrolysing the beta-lactam antibiotics to biologically inactive compounds. Their production can, therefore, greatly contribute to the clinical problem of antibiotic resistance. Three classes of beta-lactamases--A, B and C--have been identified on the basis of their amino-acid sequence; class B beta-lactamases are metalloenzymes, and are clearly distinct from members of class A and C beta-lactamases, which both contain an active-site serine residue involved in the formation of an acyl enzyme with beta-lactam substrates during catalysis. It has been predicted that class C beta-lactamases share common structural features with D,D-carboxypeptidases and class A beta-lactamases, and further, suggested that class A and class C beta-lactamases have the same evolutionary origin as other beta-lactam target enzymes. We report here the refined three-dimensional structure of the class C beta-lactamase from Citrobacter freundii at 2.0-A resolution and confirm the predicted structural similarity. The refined structure of the acyl-enzyme formed with the monobactam inhibitor aztreonam at 2.5-A resolution defines the enzyme's active site and, along with molecular modelling, indicates a mechanism for beta-lactam hydrolysis. This leads to the hypothesis that Tyr 150 functions as a general base during catalysis.     

Structure and expression of a cloned cDNA for human interleukin-2

A cDNA coding for human interleukin-2 (IL-2) has been cloned from a cDNA library prepared from partially purified IL-2 mRNA. The DNA sequence codes for a polypeptide which consists of 153 amino acids including a putative signal sequence. A biologically active polypeptide, characteristic of human IL-2, was produced when the cDNA was fused to a simian virus 40 promoter sequence and used to transfect cultured monkey COS cells.     

cDNA sequence of human apolipoprotein(a) is homologous to plasminogen

Lipoprotein(a) is an LDL-like lipoprotein whose concentration in plasma is correlated with atherosclerosis. The characteristic protein component of lipoprotein(a) is apolipoprotein(a) which is disulphide-linked to apolipoprotein B-100. Sequencing of cloned human apolipoprotein(a) complementary DNA shows that it is very similar to human plasminogen. It contains a serine protease domain and two types of plasminogen-like kringle domains, one of which is present in 37 copies.     

Primary structure homology between the product of yeast cell division control gene CDC28 and vertebrate oncogenes

In the budding yeast, Saccharomyces cerevisiae, division is controlled in response to nutrient limitation and in preparation for conjugation. Cells deprived of an essential nutrient or responding to mating pheromones cease division and become synchronous in the G1 interval, apparently constrained from completing a critical event. This event has been given the operational designation of 'start'. We have isolated a large number of start mutations which confer on S. cerevisiae cells a conditional inability to complete start (Fig. 1) presumably because they define genes which must be expressed for the start event to be successfully completed. We have described the isolation on plasmids of one of the start genes, CDC28, by genetic complementation and initial characterization of its product. We now describe the DNA sequence of the gene CDC28.     

Cloning and expression of cDNA for a human thromboxane A2 receptor.

Thromboxane A2 is a very unstable arachidonate metabolite, yet a potent stimulator of platelet aggregation and a constrictor of vascular and respiratory smooth muscles. It has been implicated as a mediator in diseases such as myocardial infarction, stroke and bronchial asthma. Using a stable analogue of this compound we recently purified the human platelet thromboxane A2 receptor to apparent homogeneity. Using an oligonucleotide probe corresponding to its partial amino-acid sequence, we have obtained a complementary DNA clone encoding this receptor from human placenta and a partial clone from cultured human megakaryocytic leukaemia cells. The placenta cDNA encodes a protein of 343 amino acids with seven putative transmembrane domains. The protein expressed in COS-7 cells binds drugs with affinities identical to those of the platelet receptor, and that in Xenopus oocytes opens Ca2(+)-activated Cl- channel on agonist stimulation. Northern blot analysis and nucleotide sequences of the two clones suggest that an identical species of the thromboxane A2 receptor is present in platelets and vascular tissues. This first report on the molecular structure of an eicosanoid receptor will promote the molecular pharmacology and pathophysiology of these bioactive compounds.     

Molecular cloning of the microtubule-associated mechanochemical enzyme dynamin reveals homology with a new family of GTP-binding proteins

A complementary DNA encoding the D100 polypeptide of rat brain dynamin--a force-producing, microtubule-activated nucleotide triphosphatase--has been cloned and sequenced. The predicted amino acid sequence includes a guanine nucleotide-binding domain that is homologous with those of a family of antiviral factors, inducible by interferon and known as Mx proteins, and with the product of the essential yeast vacuolar protein sorting gene VPS1. These relationships imply the existence of a new family of GTPases with physiological roles that may include microtubule-based motility and protein sorting.     

反复呼吸道感染患儿铁缺乏与免疫功能的关系

目的:探讨婴幼儿反复呼吸道感染与铁缺乏及免疫功能改变的相关性。方法:收集2～3岁反复呼吸道感染患儿68例,分为2组:ρ(血红蛋白)<110g/L组(A组)28例;ρ(血红蛋白)≥110g/L组(B组)40例。另设2～3岁健康儿童30例为对照组(C组)。测定红细胞碱性铁蛋白(EF)与外周血T淋巴细胞CD3+、CD4+、CD8+和免疫球蛋白IgG、IgM、IgA。结果:A、B、C3组EF平均数分别为(4 07±0 58)、(5 29±0 61)、(8 04±2 20)ag/RBC,A组低于B组,B组低于C组,具有显著统计学意义(F=77 943,P<0 01)。A、B、C3组IgG、CD4+平均数及CD4+/CD8+比值分别为[(7 54±1 02)g/L、(32 12±3 72)%、(0 89±0 35)]、[(8 32±0 63)g/L、(37 80±3 35)%、(1 10±0 17)]、[(9 14±0 94)g/L、(42 36±3 07)%、(1 46±1 12)],A组低于B组,B组低于C组,具有显著统计学意义(F=64 154,P<0 01;F=97 398,P<0 01;F=41 631,P<0 01)。A、B、C3组EF含量与CD4+及CD4+/CD8+比值呈明显的正相关关系(Rs=0 67,P<0 01;Rs=0 84,P=<0 01)。结论:铁缺乏—免疫功能损害—反复呼吸道感染之间有着密切的关系。