Mobility shift assay of calcium-binding proteins of mouse epididymal spermatozoa

Identification of a New, Testis-Specific Sperm Antigen Localized on the Principal Piece of the Spermatozoa Tail in the Fox (Vulpes vulpes)1

Fox (Vulpes vulpes) sperm antigens were identified to assess them as a potential target for a contraceptive vaccine. We report here the cloning and sequencing of fSP13, a fox sperm protein of 97 kDa. The fSP13 protein was both auto- and iso-antigenic in foxes; it was recognized by sera of foxes immunized with fox sperm proteins and vasectomized foxes. The NH2-terminal sequence of fSP13 was determined, and a piece of cDNA was amplified from testicular RNA by reverse transcription polymerase chain reaction. This piece was used to screen a cDNA library from fox testis by Southern blot. A sequence of 1662 base pairs was obtained, including a major open reading frame coding for 498 amino acid. Mass spectrometry analysis confirmed the position of the open reading frame and the presence of posttranscriptional modifications. Analysis of the predicted amino acid sequence revealed no apparent transmembrane regions. Comparison of the protein sequence with the Prosite database demonstrated the presence of four potential N-linked glycosylation sites. The fSP13 bears the closest amino acid similarity to two human sperm proteins: fibrousheathin 2 and testis-specific calcium binding protein 86-VII. The deduced 80 N-terminal amino acid sequence also presents similarity with the RIIalpha domain. By using a serum against fSP13, this antigen was localized on the principal piece of the fox spermatozoa. Northern blot analysis showed that fSP13 is specifically expressed in testis. The fSP13 is one of the first fox sperm antigens to be cloned and sequenced.

Gene expression is differentially regulated in the epididymis after orchidectomy

The epididymis is the site for the transport, maturation, and storage of spermatozoa. Regulation of epididymal structure and function is highly dependent on the ipsilateral testis. At the molecular level, however, few studies have been undertaken to determine which genes are expressed in the epididymis under testicular regulation. The goal of this study was to identify genes for which expression is regulated after orchidectomy, both throughout the epididymis and in a segment-specific manner. Microarrays spotted with 474 rat cDNAs were used to examine gene expression changes over the first 7 d post orchidectomy in the initial segment, caput, corpus, and cauda epididymidis of the adult Brown Norway rat. Using k-means cluster analysis, we show that four patterns of gene expression are activated in each epididymal segment over the first week following orchidectomy. Transient up-regulation of gene expression in the epididymis after orchidectomy is described for the first time. Potential androgen-repressed genes, including Gpx-1, show increased expression in the epididymis after orchidectomy. Several glutathione-S-transferases and calcium-binding proteins decline throughout the epididymis after orchidectomy, indicating that these may be novel androgen-regulated epididymal genes. Other genes coding for metabolism-associated proteins, transporters, and alpha-1 acid glycoprotein show segment-specific regulation in the epididymis after orchidectomy. Finally, we describe the expression of the previously uncharacterized heat shock proteins, and apoptosis-associated genes in the epididymis after orchidectomy. Thus, gene expression in the epididymis is differentially affected over time after orchidectomy. These results provide novel insight into androgen-dependent and segment-specific epididymal function.

Proteomic identification of divalent metal cation binding proteins in plant mitochondria

Divalent metal binding proteins in the Arabidopsis mitochondrial proteome were analysed by mobility shifts in the presence of divalent cations during two-dimensional diagonal sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Tandem mass spectrometry and searches of the predicted Arabidopsis protein dataset were used in an attempt to identify 34 of the proteins which shifted. This analysis identified a total of 23 distinct protein spots as the products of at least 11 different Arabidopsis genes. A series of proteins known to be divalent cation-binding proteins, or to catalyse divalent cation-dependent reactions, were identified. These included: succinyl CoA ligase beta subunit, Mn-superoxide dismutase (SOD), an Fe-S centred component of complex I and the REISKE iron-sulphur protein of the b/c(1) complex. A further set of four proteins of known function but without known divalent binding properties were also identified: the Vb subunit of cytochrome c oxidase, a subunit of ATP synthase (orfB), the acyl carrier protein, and the translocase of the outer membrane (TOM20). Three other proteins, of unknown function, were also found to shift in the presence of divalent cations. This approach has broad application for the identification of sub-proteomes based on the metal interaction of polypeptides.