Errabolu, Ramesh

ABSTRACT A human cDNA expression library was screened using anti-centrin antibodies to obtain a cDNA clone encoding human centrin. The cDNA clone contains an open reading frame of 516 base pairs and predicts a product of 172 amino acids with a calculated molecular mass of 19,528 and a pI of 4.61. Sequence analysis demonstrates that human centrin and centrins from higher plants, protozoa, algae, Xenopus and the yeast CDC31 gene product are closely related members of a subfamily of the EF-hand superfamily of calcium-binding proteins. The human centrin sequence has four putative calcium-binding domains as defined by the EF-hand consensus. Immunoprecipitation and western blot studies from HeLa cells confirm that human centrin is a protein of ∼20,000 Mr as predicted from the cDNA clone. Indirect immunofluorescence analysis of HeLa cells demonstrates that centrin is localized at the cen-trosome of interphase cells and that it redistributes to the region of the spindle poles during mitosis. When taken together with earlier genetic studies, these results demon-strate that centrin is a ubiquitous component of centro-somes and mitotic spindle poles of diverse organisms and suggest that centrin plays a role in centrosome separation at the time of mitosis.