A homolog of the serine/threonine protein kinase (p34cdc2), encoded by the cdc2+ gene of the fission yeast (Schizosaccharomyces pombe), is a catalytic subunit of maturation‐promoting factor and a key regulator of the cell cycle. We have raised a monoclonal antibody against the most conserved amino acid sequence, the PSTAIR sequence (EGVPSTAIREISLLKE) of p34cdc2 This antibody recognizes 31–34 kDa proteins by immunoblotting in all species examined so far. The proteins recognized by the anti‐PSTAIR antibody are probably either p34cdc2 itself or proteins highly homologous to p34cdc2 in the given species, since, in all species studies to date, they are all precipitated with p13suc1, the fission yeast suc1+ gene product, which binds to p34cdc2 with high specificity. The anti‐PSTAIR immunoprecipitate had no histone H1 kinase activity and did not contain cyclin B, suggesting that the PSTAIR region is masked when p34cdc2 forms a complex with cyclin B as an active kinase. Immunoblotting with the anti‐PSTAIR antibody demonstrated that the fastest‐migrating form of p34cdc2 homologues becomes abundant, when oocytes mature or the cell enters M phase. The possible significance of this observation is discussed in relation to the phosphorylation and activity state of p34cdc2 The observed broad cross‐reactivity of the anti‐PSTAIR antibody against p34cdc2 homologues in various species should permit us to examine the role of p34cdc2 homologues in the regulation of the cell cycle in a variety of organisms.
All Science Journal Classification (ASJC) codes
- Developmental Biology
- Cell Biology