Sperm Equatorial Segment Protein 1 (SPESP1)

SPESP1, encoding a deduced 350-amino acid protein.The concanavalin-A-binding protein, which the authors designated equatorial segment protein (ESP), has a predicted molecular mass of 37 kD after cleavage of a putative 19-amino acid signal peptide, and 39.6 kD prior to this posttranslational modification. The protein contains a consensus N-glycosylation site and numerous cAMP-dependent kinase, protein kinase C, and casein kinase II consensus phosphorylation sites. Northern blot analysis revealed an approximately 1.4-kb transcript only in testis. RNA dot-blot analysis confirmed expression in testis but also showed faint signals for placenta and fetal lung. Western blot analysis indicated considerable heterogeneity of posttranslationally modified forms of SPESP1.