Evolution of EF-hand calcium-modulated proteins. I. Relationships based on amino acid sequences

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Abstract
The relationships among 153 EF-hand (calcium-modulated) proteins of known amino acid sequence were determined using the method of maximum parsimony. These proteins can be ordered into 12 distinct subfamilies-calmodulin, troponin C, essential light chain of myosin, regulatory light chain, sarcoplasmic calcium binding protein, calpain, aequorin,Strongylocentrotus purpuratus ectodermal protein, calbindin 28 kd, parvalbumin, α-actinin, and S100/intestinal calcium-binding protein. Eight individual proteins-calcineurin B fromBos, troponin C fromAstacus, calcium vector protein fromBranchiostoma, caltractin fromChlamydomonas, cell-division-cycle 31 gene product fromSaccharomyces, 10-kd calcium-binding protein fromTetrahymena, LPS1 eight-domain protein fromLytechinus, and calcium-binding protein fromStreptomyces—are tentatively identified as unique; that is, each may be the sole representative of another subfamily. We present dendrograms showing the relationships among the subfamilies and uniques as well as dendrograms showing relationships within each subfamily. The EF-hand proteins have been characterized from a broad range of organismal sources, and they have an enormous range of function. This is reflected in the complexity of the dendrograms. At this time we urge caution in assigning a simple scheme of gene duplications to account for the evolution of the 600 EF-hand domains of known sequence.