Glomerulus proteome analysis with two-dimensional gel electrophoresis and mass spectrometry.

A proteome analysis of mammalian glomeruli was performed in mouse using two-dimensional-gel electrophoresis with separate Coomassie and silver staining and subsequent mass spectrometric identifications. Altogether, 414 protein spots were identified, revealing 232 different proteins representing a wide spectrum of activities, including enzymes (27%), cell-signalling proteins (22%), structural proteins (12%), protein folding and metabolism (13%), cell-growth-related proteins (6%), and replication, transcription and translation (4%). Only 53 of the proteins were detected in another proteome study, showing the value of analyses with different methodologies. However, 50 of the proteins were also identified in a proteome analysis of endothelial cells and 42 in one of glomerular mesangial cells, revealing distinct similarities between these tissues, but also unique differences. Finally, 80 of the proteins were not identified in a separate transcriptome analysis, while 10 of the present proteins were then indentifiable with genes implicated in glomerulus development and function, allowing direct correlation with expression data.

Degradation of proinsulin C-peptide in kidney and placenta extracts by a specific endoprotease activity.

Degradation of proinsulin C-peptide in mouse kidney and human placenta extracts was studied using reverse-phase high-performance liquid chromatography and nano-electrospray mass spectrometry. In total, 15 proteolytic cleavage sites were identified in human and mouse C-peptides. Early sites included the peptide bonds N-terminal of Val/Leu10, Leu12, Leu21, Leu24 and Leu26 in different combinations for the two tissues and two peptides. Notably, these cleavages were N-terminal of a hydrophobic residue, and all but one N-terminal of Leu. A late degradation product of the human peptide detected in the kidney extract was the C-terminal hexapeptide, containing just one residue more than the biologically active C-terminal pentapeptide of C-peptide. We conclude that the degradation of C-peptide in kidney and placenta follows similar patterns, dominated by endopeptidase cleavages N-terminal of Leu.

N-terminal acetylation in a third protein family of vertebrate alcohol dehydrogenase/retinal reductase found through a 'proteomics' approach in enzyme characterization.

A recent finding of a novel class of retinol-active alcohol dehydrogenase (ADH) in frog prompted analysis of this activity in other vertebrate forms. Surprisingly, yet another and still more unrelated ADH was identified in chicken tissues. It was found to be a member of the aldo-keto reductase (AKR) enzyme family, not previously known as an ADH in vertebrates. Its terminal blocking group and the N-terminal segment, not assigned by protein and cDNA structure analysis, were determined by electrospray tandem mass spectrometry after protein isolation by two-dimensional gel electrophoresis. The N terminus is Acetyl-Ala- and the N-terminal segment contains two consecutive Asn residues. The results establish the new ADH enzyme of the AKR family and show the usefulness of combined gel separation and mass spectrometry in enzyme-characterization.