Sequence analysis of the Chlamydomonas reinhardtii flagellar alpha dynein gene

Flagellar outer row dynein ATPases have been used extensively as model systems for studies of microtubule-based motility. Previously full-length sequences were only available for two of the three catalytic heavy-chain subunits (DHCs) of this enzyme. We have completed the sequence of an 18-kb genomic region encoding the Chlamydomonas reinhardtii flagellar outer row dynein alpha heavy chain. Unlike the beta- and gamma-subunits, DHC alpha is not required for assembly of other outer row dynein proteins, except for a tightly associated light chain, and thus occupies a unique position within this enzyme complex. The predicted 4,499 residue protein retains sequence homology to other dynein heavy chains throughout its central and C-terminal regions but lacks homology to any other dyneins in the first 1,000 amino acids, which may account for its unusual assembly properties. This N-terminal domain of DHC alpha contains a repetitive sequence rich in alanines, prolines, and glutamic acids. Within the more homologous C-terminal region, which includes the catalytic domain, three short sequences unique to DHC alpha may account for its specific catalytic properties and in vivo phosphorylation pattern.