Immunological identification of yeast SCO1 protein as a component of the inner mitochondrial membrane

Summary The SCO1 gene of Saccharomyces cerevisiae encodes a 30 kDa protein which is specifically required for a post-translational step in the accumulation of subunits 1 and 2 of cytochrome c oxidase (COXI and COXII). Antibodies directed against a -Gal::SCO1 fusion protein detect SCO1 in the mitochondrial fraction of yeast cells. The SCO1 protein is an integral membrane protein as shown by its resistance to alkaline extraction and by its solubilization properties upon treatment with detergents. Based on the results obtained by isopycnic sucrose gradient centrifugation and by digitonin treatment of mitochondria, SCO1 is a component of the inner mitochondrial membrane. Membrane localization is mediated by a stretch of 17 hydrophobic amino acids in the amino-terminal region of the protein. A truncated SCO1 derivative lacking this segment, is no longer bound to the membrane and simultaneously loses its biological function. The observation that membrane localization of SCO1 is affected in mitochondria of a rho ⁰ strain, hints at the possible involvement of mitochondrially coded components in ensuring proper membrane insertion.     

Human and mouse S-protein mRNA detected in Northern blot experiments and evidence for the gene encoding S-protein in mammals by Southern blot analysis

Summary Human S-protein is a serum glycoprotein that binds and inhibits the activated complement complex, mediates coagulation through interaction with antithrombin III and plasminogen activator inhibitor I, and also functions as a cell adhesion protein through interactions with extracellular matrix and cell plasma membranes. A full length cDNA clone for human S-protein was isolated from a lambda gt11 cDNA library of mRNA from the HepG2 hepatocellular carcinoma cell line using mixed oligonucleotide sequences predicted from the amino-terminal amino acid sequence of human S-protein. The cDNA clone in lambda was subcloned into pUC18 for Southern and Northern blot experiments. Hybridization with radiolabeled human S-protein cDNA revealed a single copy gene encoding S-protein in human and mouse genomic DNA. In addition, the S-protein gene was detected in monkey, rat, dog, cow and rabbit genomic DNA. A 1.7 Kb mRNA for S-protein was detected in RNA from human liver and from the PLC/PRF5 human hepatoma cell line. No S-protein mRNA was detected in mRNA from human lung, placenta, or leukocytes or in total RNA from cultured human embryonal rhabdomyosarcoma (RD cell line) or cultured human fibroblasts from embryonic lung (IMR90 cell line) and neonatal foreskin. A 1.6 Kb mRNA for S-protein was detected in mRNA from mouse liver and brain. No S-protein mRNA was detected in mRNA from mouse skeletal muscle, kidney, heart or testis.     

Formation of the transverse nerve in moth embryos : I. A scaffold of nonneuronal cells prefigures the nerve

We have studied the embryonic development of the transverse nerve (TN), an unpaired segmental nerve of the moth Manduca sexta. Two identified motor neurons and 16 identified neuroendocrine neurons project axons within the larval TN; therefore, the TN is both a peripheral nerve and a neurohaemal organ. At 33% of embryogenesis, and prior to the arrival of any neuronal growth cones, the position, shape, and trajectory of the TN are anticipated by two groups of nonneuronal cells that we call the strap and the bridge. At this time the strap and the bridge together consist of approximately 100 cells, all of which express a cell surface epitope recognized by the monoclonal antibody TN-1. As development proceeds, both the number of nonneuronal cells within the strap and the bridge and the fraction that expresses the TN-1 antigen(s) decrease. Moreover, individual cells within the strap become morphologically identifiable before the arrival of the neuronal growth cones. Most of the axons that project to the TN also express the TN-1 antigen(s) during their period of outgrowth. The two motor neuron growth cones are the first to reach the environment of the strap and the bridge, doing so at approximately 37%; having encountered these cellular structures, the growth cones restrict their navigation to this preexisting scaffolding, until they reach their muscle target. The neuroendocrine growth cones arrive later and also grow within the confines of the strap and the bridge (J.N. Carr and P.H. Taghert, 1988, Dev. Biol, 130, 500-512). In this first paper we describe the development of the strap and the bridge, and the interactions of the motor neuron growth cones with these structures. The observations are novel in documenting the extent and precision to which a peripheral nerve pathway is prefigured by a contiguous assemblage of nonneuronal cells.     

The oral assimilation of radiomanganese by the mouse

The metabolism of orally administered radiomanganese was studied in mice. Assimilation of absorbed manganese (Mn) was determined using whole body counting techniques. When⁵⁴MnCl₂ was administered, 2.7% of the dose was retained after 10 d compared with 1.2% from the⁵⁴Mn-nitrilotriacetate (NTA) complex. However, this difference was accounted for by the rapid and persistent adsorption of the Mn onto the teeth of the lower jaw when fed as the ionic salt at pH 2.0 compared with the NTA-chelate fed at pH 9.0. Once corrected for the amount adsorbed onto the teeth, the biodistribution and relative specific activity of the assimilated radiomanganese into a variety of tissues were similar for both forms of the metal.     

Geographical and temporal variation in the calls of the Manx shearwater Puffinus puffinus and British storm petrel Hydrobates pelagicus

The geographical variation in the calls of the Manx shearwater Puffinus puffinus and British storm petrel Hydrobales pelagicus was investigated, as well as its temporal stability in the shearwater. Within-island call variation was not apparent in Puffinus , although male calls were relatively more distinct locally than female calls. This is discussed in relation to the differential dispersal of the sexes. Between-island call variation was apparent in both Puffinus and Hydrobates , but the variation was continuous, and not discrete. Call divergence is unrelated to inter-island distance, and may reflect the influence of coastlines on each species'dispersal opportunities. The calls of a shearwater population changed over a period of six to seven years, apparently due to the appearance of new birds rather than surviving birds altering their calls. Male calls changed more than female calls, which, taken with dispersal factors, suggests that calls are transmitted across generations at least in part by cultural copying. The vocal'drift'over time therefore probably results from errors in this copying process.