Molecular cloning of cDNA for caltractin, a basal body-associated Ca2+-binding protein: homology in its protein sequence with calmodulin and the yeast CDC31 gene product.
An extended synthetic oligonucleotide (59-mer) was used to isolate a Chlamydomonas cDNA containing the entire coding region for a novel basal body-associated 20-kD calcium-binding protein (CaBP). DNA and RNA blot analysis indicate that the 20-kD CaBP is encoded by a single copy gene from which is derived an approximately 1.1-kb-long transcript. The deduced amino acid sequence for the protein shows a linear relatedness with calmodulin from Chlamydomonas and other organisms (45-48% identity). The primary protein sequence of the 20-kD CaBP and its predicted secondary structure suggests that the protein is likely to contain four homologous calcium-binding domains that conform to the helix-loop-helix (or EF hand) structure found in calmodulin and related calcium-modulated proteins. The major difference between the protein and calmodulin is an amino-terminal domain of 21 amino acids present on the 20-kD CaBP. In addition to its relatedness to calmodulin, the Chlamydomonas 20-kD CaBP shows a strong sequence identity (50%) with the yeast Saccharomyces cerevisiae CDC31 gene product required for spindle pole body duplication. The association of these sequence-related calcium-binding proteins to microtubule-organizing centers of divergent structure suggests a potential conserved function for the proteins.
Huang
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Department of Molecular Biology, Research Institute of Scripps Clinic, La Jolla, California 92037.
Mengersen
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Lee
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000235:genetics*; D002147:Calmodulin / Q000235:genetics; D002696:Chlamydomonas / Q000032:analysis* / Q000235:genetics; D002868:Chromosomal Proteins, Non-Histone; D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics; D004247:DNA / Q000235:genetics*; D004262:DNA Restriction Enzymes; D005656:Fungal Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D002868:Chromosomal Proteins, Non-Histone; D003062:Codon; D005656:Fungal Proteins; C056608:caltractin; D004247:DNA; D004262:DNA Restriction Enzymes