Cdc31s

Cdc31s are centrin family proteins, a group of small calcium-binding proteins that are conserved across many eukaryotes. The term Cdc31 traditionally refers to a centrin in the budding yeast Saccharomyces cerevisiae, where the protein is essential for proper cell division. In broader use, Cdc31s denotes orthologs and paralogs of this centrin in other species, which share a common structural framework and related functions in centrosome or basal body assembly.

In budding yeast, Cdc31 plays a critical role in spindle pole body (SPB) duplication, a process equivalent to centrosome duplication in other organisms. Cdc31 localizes to SPBs and participates in the assembly of the half-bridge structure that connects SPBs during duplication. It forms functional interactions with other SPB components, notably Kar1, to initiate a new SPB during the cell cycle. Loss or malfunction of Cdc31 disrupts SPB duplication, leading to cell cycle arrest or defects in chromosome segregation.

Cdc31s are characterized by their calmodulin-like fold and EF-hand calcium-binding motifs, typically enabling calcium-responsive interactions with partner proteins. Although the core structure is conserved, sequence variation among species gives rise to functional specializations in SPB assembly, centrosome maintenance, or basal body function. Their calcium-binding properties contribute to conformational changes that regulate binding to targets such as Kar1 or Sfi1 in the SPB milieu.

Across organisms, centrins similar to Cdc31s participate in centrosome or centriole-related processes, often linked to organelle duplication and stability. The study of Cdc31s in yeast provides a model for understanding how calcium-binding proteins coordinate complex multiprotein assemblies at critical cell-cycle milestones.