Maize cap1 encodes a novel SERCA-type calcium-ATPase with a calmodulin-binding domain.
A cDNA (CAP1) isolated from maize roots shares sequence identity with genes encoding P-type Ca(2+)-ATPases and restores the growth phenotype of yeast mutants defective in Ca(2+)-pumps. CAP1 was transcribed and translated in the yeast mutant. Furthermore, the membrane-integrated product formed a Ca(2+)-dependent phosphorylated intermediate and supported Ca(2+) transport. Although CAP1 shares greater sequence identity with mammalian "endoplasmic reticulum-type" Ca(2+)-pumps, it differs from these genes by having features of calmodulin (CaM)-regulated Ca(2+)-pumps. CAP1 from yeast microsomes bound CaM, and the CAP1-dependent Ca(2+) transport in yeast was stimulated by CaM. Peptides from the C terminus of CAP1 bound CaM. Anti-CAP1 antibodies specifically recognized a maize microsomal polypeptide that also bound CaM. A similar polypeptide also formed a Ca(2+)-dependent phosphoenzyme. Our results suggest that cap1 encodes a novel form of CaM-regulated Ca(2+)-ATPase in maize. CAP1 appears to be encoded by one or two genes in maize. CAP1 RNA is induced only during early anoxia, indicating that the Ca(2+)-pump may play an important role in O(2)-deprived maize cells.
Subbaiah
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Department of Crop Sciences, University of Illinois, Urbana and the United States Department of Agriculture/Agricultural Research Service, Soybean/Maize Germplasm, Pathology and Genetics Unit, Urbana, Illinois 61801, USA. subbaiah@uiuc.edu
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D000595:Amino Acid Sequence; D001665:Binding Sites; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli; D007700:Kinetics; D008969:Molecular Sequence Data; D012275:Oryza / Q000201:enzymology; D010940:Plant Proteins; D018517:Plant Roots / Q000201:enzymology; D014176:Protein Biosynthesis; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics*
D002147:Calmodulin; D010940:Plant Proteins; D011994:Recombinant Proteins; C411879:cap1 protein, Zea mays; D000252:Calcium-Transporting ATPases