The protein complexity of the cytoskeleton of bovine and human sperm heads: the identification and characterization of cylicin II

Exp Cell Res. 1995 May;218(1):174-82. doi: 10.1006/excr.1995.1145.


The cytoskeletal calyx of mammalian sperm heads surrounding the basolateral part of the nucleus contains two kinds of basic proteins: Calicin, a polypeptide of approximate M(r) 60,000 as estimated from SDS-PAGE, and the group of the very basic cylicins (pI > 10.0), formerly designated as "multiple-band polypeptides." Recently, bovine cylicin I has been cDNA cloned and identified as a new type of a cytoskeletal protein, which contains numerous Lys-Lys-Asp tripeptides accumulated in nine central repetitive units predicted to form alpha-helices. We now report the cDNA cloning and localization of a second species of cylicin, bovine cylicin II, present in bovine and human sperm heads: Cylicin II (488 amino acids, M(r) 53,561, pI 10.55) shows the same prominent molecular characteristics as cylicin I, including a high content of charged amino acids, the abundance of Lys-Lys-Asp tripeptides, and repetitive units of presumably alpha-helical configuration, but also presents some differences. As with cylicin I mRNA, the 2.6-kb mRNA has also been shown to be specifically expressed in testis. The possible existence of a larger cylicin multigene family and its contribution to the cytoskeleton and the morphogenesis of the sperm head are discussed.

Publication types

  • Comparative Study

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cattle
  • Cytoskeletal Proteins / analysis
  • Cytoskeletal Proteins / biosynthesis*
  • Cytoskeletal Proteins / chemistry*
  • DNA, Complementary
  • Gene Library
  • Humans
  • Male
  • Molecular Sequence Data
  • Protein Structure, Secondary
  • Sequence Homology, Amino Acid
  • Sperm Head / chemistry
  • Sperm Head / metabolism*


  • CYLC2 protein, Bos taurus
  • Cytoskeletal Proteins
  • DNA, Complementary
  • cylicin protein, Bos taurus

Associated data

  • GENBANK/Z46788
  • GENBANK/Z46789