Sperm Flagellar Protein 1 (SPEF1)

The 234-amino acid mouse protein has a predicted molecular mass of 27 kD. Database analysis identified a human C20ORF28 homolog as a 236-amino acid protein with a predicted molecular mass of 18.4 kD.

Human and mouse CLAMP both have an N-terminal domain with similarity to a calponin homology (CH) domain and a C-terminal coiled-coil domain, and they share 88% amino acid identity. Northern blot analysis detected a 1.6-kb mouse transcript with highest expression in testis, followed by brain, kidney, and lung, and a 2.2-kb mouse transcript in testis only. Western blot analysis detected rat Clamp protein in brain, lung, and testis. Immunofluorescence of whole-mount mouse cochlea and immunogold electron microscopy localized mouse Clamp throughout microtubule bundles in pillar cells.