We surveyed genome sequences from the basidiomycetous mushroom Coprinopsis cinerea and isolated a cDNA homologous to CMKA, a calmodulin-dependent protein kinase (CaMK) in Aspergillus nidulans. We designated this sequence, encoding 580 amino acids with a molecular weight of 63,987, as CoPK02. CoPK02 possessed twelve subdomains specific to protein kinases and exhibited 43, 35, 40% identity with rat CaMKI, CaMKII, CaMKIV, respectively, and 40% identity with CoPK12, one of the CaMK orthologs in C. cinerea. CoPK02 showed significant autophosphorylation activity and phosphorylated exogenous proteins in the presence of Ca2+/CaM. By the CaM-overlay assay we confirmed that the C-terminal sequence (Trp346-Arg358) was the calmodulin-binding site, and that the binding of Ca2+/CaM to CoPK02 was reduced by the autophosphorylation of CoPK02. Since CoPK02 evolved in a different clade from CoPK12, and showed different gene expression compared to that of CoPK32, which is homologous to mitogen-activated protein kinase-activated protein kinase, CoPK02 and CoPK12 might cooperatively regulate Ca2+-signaling in C. cinerea.
Keywords: Ca2+/calmodulin-dependent protein kinase; CaM: calmodulin; CaMK: Ca2+/calmodulin protein kinase; Coprinopsis cinerea; GRAVY: grand average of hydropathy; KD: kinase dead type; MAPKAPK: mitogen-activated protein kinase-activated protein kinase; MBP: myelin basic protein; MLC: myosin light chain; NJ: neighbor-joining; PPase: protein phosphatase; WT: wild type; mushroom; protein phosphorylation.