Two Additional Salmonella Serotypes: Salmonella enteritidis Ser 58:a:- and Salmonella enteritidis Ser 44Z36, Z38:-

The antigenic compositions of two additional Salmonella serotypes isolated from the feces of man were determined to be 58:a:- and 44:Z(36), Z(38)-.     

Identification of functional domains in the RAD51L2 (RAD51C) protein and its requirement for gene conversion

The RAD51 protein plays a key part in the process of homologous recombination through its catalysis of homologous DNA pairing and strand exchange. Additionally five novel mammalian RAD51-like proteins have been identified in mammalian cells, but their roles in homologous recombination are much less well established. These RAD51-like proteins form two different complexes, but only the RAD51L2 (RAD51C) protein is a part of both complexes. By using site-directed mutagenesis of RAD51L2, we show that non-conservative mutation of the putative ATP-binding domain severely reduces its function, whereas a conservative mutation shows partial loss of function. We find that the protein is localized to the nucleus by tagging RAD51L2 with the green fluorescent protein and provisionally identify a C-terminal domain that acts as a nuclear localization signal. Further, a RAD51L2-deficient cell line was found to have significantly reduced homology-directed repair of a DNA double-strand break by gene conversion. This recombination defect could be partially restored by ectopic expression of the human RAD51L2 protein. Therefore we have identified protein domains that are important for the correct functioning of RAD51L2 and have shown that there is a specific requirement for RAD51L2 in gene conversion in mammalian cells.     

Molecular targeting of inhibitor of apoptosis proteins based on small molecule mimics of natural binding partners

An assay based on a solvent-sensitive fluorogenic dye molecule, badan, is used to test the binding affinity of a library of tetrapeptide molecules for the BIR3 (baculovirus IAP repeat) domain of XIAP (X-linked inhibitor of apoptosis protein). The fluorophore is attached to a tetrapeptide, Ala-Val-Pro-Cys-NH(2), through a thiol linkage and, upon binding to XIAP, undergoes a solvatochromic shift in fluorescence emission. When a molecule (e.g., a natural protein known to bind to XIAP or a tetrapeptide mimic) displaces the dye, the emission shifts back to the spectrum observed in water. As emission intensity is related to the binding of the tetrapeptide, the intensity can be used to determine the equilibrium constant, K, for the displacement of the dye by the tetrapeptide. The results permit residue-specific analysis of the interaction. Furthermore, we show that hydrophobic effects in the fourth position are general and can effectively increase overall affinity.     

Molecular organization of amyloid protofilament-like assembly of betabellin 15D: helical array of beta-sandwiches

Betabellin is a 32-residue peptide engineered to fold into a four-stranded antiparallel beta-sheet protein. Upon air oxidation, the betabellin peptides can fold and assemble into a disulfide-bridged homodimer, or beta-sandwich, of 64 residues. Recent biophysical and ultrastructural studies indicate that betabellin 15D (B15D) (a homodimer of HSLTAKIpkLTFSIAphTYTCAVpkYTAKVSH, where p = DPro, k = DLys, and h = DHis) forms unbranched, 35-A wide assemblies that resemble the protofilaments of amyloid fibers. In the present study, we have analyzed in detail the X-ray diffraction patterns of B15D prepared from acetonitrile. The fiber diffraction analysis indicated that the B15D fibril was composed of a double helix defined by the selection rule l = n + 7m (where l is even, and n and m are any integers), and having a 199-A period and pitch, 28-A rise per unit, and 10-A radius. This helical model is equivalent to a reverse-handed, single helix with half the period and defined by the selection rule l = -3n + 7m (where l is any integer). The asymmetric unit is the single B15D beta-sandwich molecule. These results suggest that the betabellin assembly that models the protofilaments of amyloid fibers is made up of discrete subunits on a helical array. Multiple intersheet hydrogen bonds in the axial direction and intersandwich polar interactions in the lateral direction stabilize the array.     

ProDom: automated clustering of homologous domains

The ProDom database is a comprehensive set of protein domain families automatically generated from the SWISS-PROT and TrEMBL sequence databases. An associated database, ProDom-CG, has been derived as a restriction of ProDom to completely sequenced genomes. The ProDom construction method is based on iterative PSI-BLAST searches and multiple alignments are generated for each domain family. The ProDom web server provides the user with a set of tools to visualise multiple alignments, phylogenetic trees and domain architectures of proteins, as well as a BLAST-based server to analyse new sequences for homologous domains. The comprehensive nature of ProDom makes it particularly useful to help sustain the growth of InterPro.     

Call type signals caller goal: a new take on ultimate and proximate influences in vocal production

After 40 years of debate it remains unclear whether signallers produce vocalizations in order to provide receivers with information about call context or external stimuli. This has led some researchers to propose that call production is arousal‐ or affect‐based. Although arousal influences certain acoustic parameters within a call type, we argue that it cannot explain why individuals across vertebrates produce different call types. Given emerging evidence that calls are goal‐based, we argue that call type is a signal of a caller's goal to elicit a change in receiver behaviour. Using chimpanzees (Pan troglodytes) and vervet monkeys (Cercopithecus aethiops) as case studies, we demonstrate the two benefits of viewing call production as signalling both caller goal (which determines call type) and caller arousal (which affects within‐call‐type variation). Such a framework can explain first, why a single class of calls is apparently given in multiple contexts, and, second, why some species have larger call repertoires than others. Previous studies have noted links between sociality and repertoire size, but have not specified exactly why animals living in societies that are more complex might require a greater number of differentiated signals. The caller‐goal framework potentially clarifies how social complexity might favour call diversification. As social complexity increases, callers may need to elicit a larger number of distinct behaviours from a wider range of distinct audiences.     

Involvement of glycogen synthase kinase-3beta and tau phosphorylation in neuronal Golgi disassembly

The dissociation of the neuronal Golgi complex is a classical feature observed in neurodegenerative disorders including Alzheimer's disease. The goal of this study is to determine if the phosphorylation of tau protein is involved in neuronal Golgi disassembly. Primary cortical cultures were exposed to two Golgi toxins, brefeldin A (BFA) or nordihydroguaiaretic acid (NDGA). Immunocytochemical studies using the anti58 k antibody revealed that Golgi disassembly started in exposed neurons a few minutes after treatment. BFA and NDGA induced a rapid and transient increase in tau phosphorylation in a site-specific manner on immunoblots. In addition, the increase in tau phosphorylation directly correlated with a transient dissociation of tau from the cytoskeleton and a decrease of the acetylated tubulin. Furthermore, the activity of glycogen synthase kinase-3beta (GSK-3beta) increased transiently, as demonstrated by the kinase activity assay and by immunoblottings of serine-9 and tyrosine-216 phosphorylated of GSK-3beta. A decrease of the Akt phosphorylated form was also shown. The increase in tau phosphorylation was inhibited by the GSK-3beta inhibitor, lithium. Finally, morphometric studies showed that lithium partially blocked the Golgi disassembly caused by BFA or NDGA. Together these findings indicate that GSK-3beta activity and tau phosphorylation state are involved in the maintenance of the neuronal Golgi organization.