The M = 8,000 and 11,000 Outer Arm Dynein Light Chains from Chlamydomonas Flagella Have Cytoplasmic Homologues

Abstract

We report here the molecular cloning of the M(r) = 8,000 and 11,000 dynein light chains (DLCs) from the outer arm of Chlamydomonas flagella. These two molecules, which are associated with the intermediate chains at the base of the soluble dynein particle, have predicted masses of 10.3 and 13.8 kDa, respectively, and are 40% identical. Southern blot analysis indicates that one gene exists for each DLC in the Chlamydomonas genome and only a single message was observed for each on Northern blots. Secondary structure predictions suggest that both molecules contain a highly amphiphilic alpha helix that is presumably involved in protein-protein interactions. Several DLC homologues were identified in the GenBank databases. One, predicted from the genomic sequence of Caenorhabditis elegans, is 88.8% identical with the M(r) = 8,000 Chlamydomonas DLC. A second, from rice callus cDNA, is 47% identical with the same DLC. As neither nematodes nor higher plants have motile cilia or flagella at any stage of their life cycles, these DLC homologues presumably must function within the cytoplasm where they may represent previously unrecognized components of cytoplasmic dynein.