Calcium Binding Is Required for Calmodulin Function in Aspergillus nidulans
AUTOR(ES)
Joseph, James D.
FONTE
American Society for Microbiology
RESUMO
To explore the structural basis for the essential role of calmodulin (CaM) in Aspergillus nidulans, we have compared the biochemical and in vivo properties of A. nidulans CaM (AnCaM) with those of heterologous CaMs. Neither Saccharomyces cerevisiae CaM (ScCaM) nor a Ca2+ binding mutant of A. nidulans CaM (1234) interacts appreciably with A. nidulans CaM binding proteins by an overlay assay or activates two essential CaMKs, CMKA and CMKB. In contrast, although vertebrate CaM (VCaM) binds a spectrum of proteins similar to that for AnCaM, it is unable to fully activate CMKA and CMKB, displaying a higher KCaM and reduced Vmax for both enzymes. In correlation with the biochemical analysis, neither ScCaM nor 1234 can support A. nidulans growth in the absence of the endogenous protein, whereas VCaM only partially complements the absence of wild-type CaM. Analysis of VCaM and AnCaM chimeras demonstrates that amino acid variations in both N- and C-terminal domains contribute to the inability of VCaM to activate CMKB, but differences in the N terminus are largely responsible for the reduced activity towards CMKA. In vivo, the chimeric molecules support growth equivalently, but only to levels intermediate between those of VCaM and AnCaM, suggesting that the reduced ability to activate the CaMKs is not solely responsible for the inability of VCaM to complement the absence of the wild-type protein. Thus, not only is Ca2+ binding required for CaM function in A. nidulans, but the essential in vivo functions of A. nidulans CaM are uniquely sensitive to the subtle amino acid variations present in vertebrate CaM.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=118048Documentos Relacionados
- Ca(2+)/calmodulin-dependent kinase is essential for both growth and nuclear division in Aspergillus nidulans.
- Calmodulin-dependent multifunctional protein kinase in Aspergillus nidulans.
- Aspergillus nidulans verA is required for production of the mycotoxin sterigmatocystin.
- The tamA gene of Aspergillus nidulans contains a putative zinc cluster motif which is not required for gene function.
- Aspergillus nidulans stcP encodes an O-methyltransferase that is required for sterigmatocystin biosynthesis.