Identification of a novel testis-specific member of the phosphatidylethanolamine binding protein family, pebp-2.
The phosphatidylethanolamine binding proteins (pebps) are an evolutionarily conserved family of proteins recently implicated in mitogen-activated protein (MAP) kinase pathway regulation, where they are called raf kinase inhibitory proteins. Here, we describe the cloning, cellular localization, and partial characterization of a new member, pebp-2, with potential roles in male fertility. Expression data show that pebp-2 is a testis-specific 21-kDa protein found within late meiotic and haploid germ cells in a stage-specific pattern that is temporally distinct from that of pebp-1. Sequence analyses suggest that pebp-2 forms a distinct subset of the pebp family within mammals. Database analyses revealed the existence of a third subset. Analysis suggests that the specificity/regulation of the distinct pebps subsets is likely to be determined by the amino terminal 40 amino acids or the 3' untranslated region, where the majority of sequence differences occur. Protein homology modeling suggests that pebp-2 protein is, however, topologically similar to other pebps and composed of Greek key fold motifs, a dominant beta-sheet formed from five anti-parallel beta strands forming a shallow groove associated with a putative phosphatidylethanolamine binding site. The pebp-2 gene is intronless and data suggest that it is a retrogene derived from pebp-1. Further, pebp-2 colocalizes with members of the MAP kinase pathway in late spermatocytes and spermatids and on the midpiece of epididymal sperm. These data raise the possibility that pebp-2 is a novel participant in the MAP kinase signaling pathway, with a role in spermatogenesis or posttesticular sperm maturation.
Monash Institute of Reproduction and Development, Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Clayton, Victoria 3168, Australia.
Deborah M
DM
Hickox
Gerard
G
Gibbs
John R
JR
Morrison
Kim
K
Sebire
Kim
K
Edgar
Hooi-Hong
HH
Keah
Kerina
K
Alter
Kate L
KL
Loveland
Milton T W
MT
Hearn
David M
DM
de Kretser
Moira K
MK
O'Bryan
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics; D002417:Cattle; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry; D005298:Fertility; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D037102:Lectins; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases / Q000032:analysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010714:Phosphatidylethanolamines / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013094:Spermatozoa / Q000737:chemistry; D013737:Testis / Q000737:chemistry*
D002352:Carrier Proteins; D018076:DNA, Complementary; D037102:Lectins; C471030:Pbp2 protein, mouse; D010714:Phosphatidylethanolamines; D012333:RNA, Messenger; D020928:Mitogen-Activated Protein Kinases