Jelly belly protein activates the receptor tyrosine kinase Alk to specify visceral muscle pioneers

The secreted protein Jelly belly (Jeb) is required for an essential signalling event in Drosophila muscle development. In the absence of functional Jeb, visceral muscle precursors are normally specified but fail to migrate and differentiate. The structure and distribution of Jeb protein implies that Jeb functions as a signal to organize the development of visceral muscles. Here we show that the Jeb receptor is the Drosophila homologue of anaplastic lymphoma kinase (Alk), a receptor tyrosine kinase of the insulin receptor superfamily. Human ALK was originally identified as a proto-oncogene, but its normal function in mammals is not known. In Drosophila, localized Jeb activates Alk and the downstream Ras/mitogen-activated protein kinase cascade to specify a select group of visceral muscle precursors as muscle-patterning pioneers. Jeb/Alk signalling induces the myoblast fusion gene dumbfounded (duf; also known as kirre) as well as org-1, a Drosophila homologue of mammalian TBX1, in these cells.     

A close halo of large transparent grains around extreme red giant stars

An intermediate-mass star ends its life by ejecting the bulk of its envelope in a slow, dense wind. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust, which is then accelerated by radiation pressure, entraining the gas and driving the wind. Explaining the amount of mass loss, however, has been a problem because of the difficulty of observing tenuous gas and dust only tens of milliarcseconds from the star. For this reason, there is no consensus on the way sufficient momentum is transferred from the light from the star to the outflow. Here we report spatially resolved, multiwavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the Hertzsprung-Russell diagram. When imaged in scattered light, dust shells were found at remarkably small radii (less than about two stellar radii) and with unexpectedly large grains (about 300 nanometres in radius). This proximity to the photosphere argues for dust species that are transparent to the light from the star and, therefore, resistant to sublimation by the intense radiation field. Although transparency usually implies insufficient radiative pressure to drive a wind, the radiation field can accelerate these large grains through photon scattering rather than absorption--a plausible mass loss mechanism for lower-amplitude pulsating stars.     

Apolactoferrin structure demonstrates ligand-induced conformational change in transferrins

Proteins of the transferrin family, which contains serum transferrin and lactoferrin, control iron levels in higher animals through their very tight (Kapp approximately 10(20)) but reversible binding of iron. These bilobate molecules have two binding sites, one per lobe, each housing one Fe3+ and the synergistic CO3(2-) ion. Crystallographic studies of human lactoferrin and rabbit serum transferrin in their iron-bound forms have characterized their binding sites and protein structure. Physical studies show that a substantial conformational change accompanies iron binding and release. We have addressed this phenomenon through crystal structure analysis of human apolactoferrin at 2.8 A resolution. In this structure the N-lobe binding cleft is wide open, following a domain rotation of 53 degrees, mediated by the pivoting of two helices and flexing of two interdomain polypeptide strands. Remarkably, the C-lobe cleft is closed, but unliganded. These observations have implications for transferrin function and for binding proteins in general.     

Action spectra for bilirubin photodisappearance

Summary The excitation wavelength dependence of bilirubin photodestruction, as measured by quantum yields, has been determined in benzene, chloroform-1% ethanol, chloroform-1% hexane, methanol-1% concentrated ammonia, pH 8.5 aqueous buffer and pH 7.4 aqueous buffer with added albumin. The results show that in the visible spectrum the 370–490 nm excitation wavelength region is very effective in the photodestruction, but excitation in the UV-region (<320 nm) is even more effective.The authors wish to thank the National Science Foundation (CHE 74-20877) and the National Institute of Child Health (HD 09026) for the generous support of this work.     

A disc-electrophoresis investigation of certain characteristics of Triton X-100 solubilized proteins from malePeriplaneta americana

Resumen Un agregado de proteínas solubilizadas en Triton X-100 fue resuelto como una banda por electroforesis a un pH de 8.5. En un pH de 7.1 estas fracciones no demuestran el efecto de agregación. Solamente electroforesis conTris/glicina como amortiguador y concentraciones del detergente menor de 0.6% dieron resultados.