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Robert J Beynon

Publications and source records attributed to Robert J Beynon.

24 records · Page 2Linked to original sources
PubMed2004

Urinary proteins and the modulation of chemical scents in mice and rats.

The urine of mice, rats and some other rodents contains substantial quantities of proteins that are members of the lipocalin family. The proteins are thought to be responsible for the binding and release of low molecular weight pheromones, and there is now good evidence that they discharge this role, providing a slow release mechanism for volatile components of scent marks. However, the proteins may function as chemosignalling molecules in their own right, contributing one or more roles in the communication of individual identity and scent mark ownership. In this review, we summarize current understanding of the structure and function of these urinary proteins, and speculate about their role as supporters or as key participants in the elaboration of the complex chemosensory properties of a rodent scent mark.

Amino Acid Sequence↗
PubMed2003

Proteome analysis of intact proteins in complex mixtures.

Analysis of intact protein mixtures by electrospray ionization mass spectrometry requires the resolution of a complex, overlapping set of multiply charged envelopes. To ascertain the ability of a moderate resolution mass spectrometer to resolve such mixtures, we have analyzed the soluble proteins of adult chick skeletal muscle. This is a highly specialized tissue showing a marked bias in expression of glycolytic enzymes in the soluble fraction. SDS-PAGE-resolved proteins were first identified by a combination of matrix-assisted laser desorption ionization time-of-flight (TOF) and electrospray ionization tandem mass spectrometry. Then the mixture of intact proteins was introduced into the electrospray source of a Q-TOF mass spectrometer either by direct infusion or via a C4 desalting trap. In both instances, the complex pattern of peaks could be resolved into true masses, and these masses could in many instances be reconciled with the masses predicted from the known protein sequences when qualified by expected co- and post-translational modifications. These included loss of the N-terminal initiator methionine residue and N-terminal acetylation. The ability to resolve such a complex mixture of proteins with a routine instrument is of considerable value in analyses of protein expression and in the confirmation of post-translational changes in mature proteins.

Amino Acid Sequence↗
PubMed2002

Stable isotope labelling in vivo as an aid to protein identification in peptide mass fingerprinting.

Peptide mass fingerprinting (PMF) is a powerful technique for identification of proteins derived from in-gel digests by virtue of their matrix-assisted laser desorption/ionization-time of flight mass spectra. However, there are circumstances where the under-representation of peptides in the mass spectrum and the complexity of the source proteome mean that PMF is inadequate as an identification tool. In this paper, we show that identification is substantially enhanced by inclusion of composition data for a single amino acid. Labelling in vivo with a stable isotope labelled amino acid (in this paper, decadeuterated leucine) identifies the number of such amino acids in each digest fragment, and show a considerable gain in the ability of PMF to identify the parent protein. The method is tolerant to the extent of labelling, and as such, may be applicable to a range of single cell systems.

Deuterium↗
PubMed2002

Polymorphism in major urinary proteins: molecular heterogeneity in a wild mouse population.

Major urinary proteins (MUPs) are present in high levels in the urine of mice, and the specific profile of MUPs varies considerably among wild-caught individuals. We have conducted a detailed study of the polymorphic variation within a geographically constrained island population, analyzing the MUP heterogeneity by isoelectric focusing and analytical ion exchange chromatography. Several MUPs were purified in sufficient quantities for analysis by electrospray ionization mass spectrometry and MALDI-TOF mass spectrometry of endopeptidase Lys-C peptide maps. The results of such analyses permitted the identification of three new MUP allelic variants. In each of these proteins, the sites of variation were located to a restricted segment of the polypeptide chain, projecting to a patch on the surface of the protein, and connected to the central lipocalin calyx through the polypeptide backbone. The restriction of the polymorphic variation to one segment of the polypeptide may be of functional significance, either in the modulation of ligand release or in communication of individuality signals within urinary scent marks.

Animal Communication↗
PubMed2002

Dynamics of protein turnover, a missing dimension in proteomics.

Functional genomic experiments frequently involve a comparison of the levels of gene expression between two or more genetic, developmental, or physiological states. Such comparisons can be carried out at either the RNA (transcriptome) or protein (proteome) level, but there is often a lack of congruence between parallel analyses using these two approaches. To fully interpret protein abundance data from proteomic experiments, it is necessary to understand the contributions made by the opposing processes of synthesis and degradation to the transition between the states compared. Thus, there is a need for reliable methods to determine the rates of turnover of individual proteins at amounts comparable to those obtained in proteomic experiments. Here, we show that stable isotope-labeled amino acids can be used to define the rate of breakdown of individual proteins by inspection of mass shifts in tryptic fragments. The approach has been applied to an analysis of abundant proteins in glucose-limited yeast cells grown in aerobic chemostat culture at steady state. The average rate of degradation of 50 proteins was 2.2%/h, although some proteins were turned over at imperceptible rates, and others had degradation rates of almost 10%/h. This range of values suggests that protein turnover is a significant missing dimension in proteomic experiments and needs to be considered when assessing protein abundance data and comparing it to the relative abundance of cognate mRNA species.

Amino Acids↗