title: A bacterial calcium-binding protein homologous to calmodulin.
abstract: Many of the effects of calcium ions in eukaryotic cells are mediated by calcium-binding regulatory proteins such as calmodulin, in which each calcium-binding site has a distinctive helix-loop-helix conformation termed the EF hand. Protein S from the spore coat of the Gram-negative bacterium Myxococcus xanthus has been shown to resemble calmodulin in its internally-duplicated structure and ability to bind calcium. However, it has a beta-sheet secondary structure rather than the helix-loop-helix arrangement of the eukaryotic proteins. We have determined the complete amino-acid sequence of a calcium-binding protein from the Gram-positive bacterium "Streptomyces erythraeus" by cloning and sequencing the corresponding gene. It contains four EF-hand motifs bearing remarkable sequence similarity to the calcium-binding sites in calmodulin. This implies that the EF-hand super-family may have evolved from ancient proteins present in prokaryotes.
mesh_terms: D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000235:genetics*; D002147:Calmodulin / Q000235:genetics*; D005796:Genes; D006801:Humans; D011487:Protein Conformation; D012689:Sequence Homology, Nucleic Acid; D013302:Streptomyces / Q000235:genetics*
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin