title: Comparative genomics of the sperm mitochondria-associated cysteine-rich protein gene.
abstract: The sperm mitochondrial cysteine-rich protein (SMCP) is a rapidly evolving cysteine- and proline-rich protein that is localized in the mitochondrial capsule and enhances sperm motility. The sequences of the SMCP protein, gene, and mRNA in a variety of mammals have been compared to understand their evolution and regulation. SMCP can now be reliably identified by its tripartite structure including a short amino-terminal segment; a central segment containing short tandem repeats rich in cysteine, proline, glutamine, and lysine; and a C-terminal segment containing no repeats, few cysteines, and a C-terminal lysine. The SMCP gene is located in the epidermal differentiation complex (EDC), a large gene cluster that functions in forming epithelial barriers. Similarities in chromosomal location, molecular function, intron-exon structure, and protein organization argue that SMCP originated from an EDC gene and acquired spermatogenic cell-specific transcriptional and translational regulation and a novel cellular function in sperm motility. The SMCP 5' UTR and 3' UTR contain conserved elements and uORFs that may function in cytoplasmic regulation of gene expression, and the levels of SMCP mRNA in human are much lower than in other mammals, a feature of male-biased expression. The evolution of SMCP has been accompanied by changes in the sequence, number, and length of repeat units, including three alleles in dogs. The major proteins associated with the mitochondrial capsule, SMCP and phospholipid hydroperoxide glutathione peroxidase, provide outstanding examples of changes in cellular function driven by selective pressures on sperm motility, an important determinant of male reproductive success.
authors.affiliation: Department of Biology, University of Massachusetts at Boston, 100 Morrissey Boulevard, Boston, MA 02125, USA.
authors.forename: Sabrina K
authors.initials: SK
authors.lastname: Hawthorne
authors.forename: Golnaz
authors.initials: G
authors.lastname: Goodarzi
authors.forename: Jana
authors.initials: J
authors.lastname: Bagarova
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Gallant
authors.forename: Rakhee R
authors.initials: RR
authors.lastname: Busanelli
authors.forename: Wendy J
authors.initials: WJ
authors.lastname: Olend
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Kleene
mesh_terms: D020413:3' Untranslated Regions / Q000235:genetics; D020121:5' Untranslated Regions / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002417:Cattle; D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D006224:Cricetinae; D030561:Databases, Nucleic Acid; D004285:Dogs; D004848:Epithelium / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D023281:Genomics / Q000379:methods*; D006801:Humans; D008297:Male; D008647:Mesocricetus; D051379:Mice; D008969:Molecular Sequence Data; D010542:Peromyscus; D011544:Pseudogenes / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051140:Selenoproteins / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013737:Testis / Q000378:metabolism; D024363:Transcription Initiation Site
chemical_list: D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D012333:RNA, Messenger; D051140:Selenoproteins