Cdc31p

Cdc31p is a centrin family calcium-binding protein in the budding yeast Saccharomyces cerevisiae, encoded by the CDC31 gene. It is the yeast homolog of centrins and is a small EF-hand protein implicated in the duplication of the spindle pole body (SPB), the yeast equivalent of the centrosome.

Cdc31p localizes to the SPB throughout the cell cycle, with enrichment at the site of SPB duplication. It is essential for SPB duplication, and loss or impairment of Cdc31p leads to defects that prevent proper SPB duplication, often resulting in monopolar spindles and cell cycle arrest.

Mechanistically, Cdc31p participates in forming the SPB half-bridge, a structure required to template the separation of the mother and daughter SPBs. It forms a functional complex with Sfi1p, and this Sfi1p–Cdc31p bridge is thought to drive the assembly and elongation of the duplication pathway. Kar1p, another SPB component, interacts with Cdc31p, supporting the bridge-based duplication process.

Cdc31p contains EF-hand calcium-binding motifs, and calcium binding modulates its interactions with partner proteins. Its activity is coordinated with the cell cycle, consistent with the timing of SPB duplication during late mitosis or early G1.

Genetically, CDC31 is essential for viability in S. cerevisiae. Centrin proteins are broadly conserved in eukaryotes and generally participate in centrosome or SPB duplication and microtubule organization, with Cdc31p representing the yeast-specific centrins at the SPB rather than centrioles. Related topics include centrins, SPB, Sfi1p, and Kar1p.