Chlamydomonas Flagellar Outer Row Dynein Assembly Protein Oda7 Interacts with Both Outer Row and I1 Inner Row Dyneins

Judy Freshour,Ruth Yokoyama,David R Mitchell

doi:10.1074/jbc.m607509200

Abstract

We previously found that a mutation at the ODA7 locus in Chlamydomonas prevents axonemal outer row dynein assembly by blocking association of heavy chains and intermediate chains in the cytoplasm. We have now cloned the ODA7 locus by walking in the Chlamydomonas genome from nearby molecular markers, confirmed the identity of the gene by rescuing the mutant phenotype with genomic clones, and identified the ODA7 gene product as a 58-kDa leucine-rich repeat protein unrelated to outer row dynein LC1. Oda7p is missing from oda7 mutant flagella but is present in flagella of other outer row or inner row dynein assembly mutants. However, Oda7 levels are greatly reduced in flagella that lack both outer row dynein and inner row I1 dynein. Biochemical fractionation and rebinding studies support a model in which Oda7 participates in a previously uncharacterized structural link between inner and outer row dyneins.

Highlights

Flagellar dyneins fall into two broad groups: outer row dyneins, which are essential for maintaining normal beat frequency and for some calcium-dependent waveform changes, and inner row dyneins, which are needed for normal waveform and for some tactic responses [10]
The docking complex consists of three proteins that assemble on the doublet surface separately from the motor complex [14]
Inner row dyneins are thought to be regulated in part through the action of regulatory complexes such as radial spokes and the dynein regulatory complex, which do not appear to come into close contact with the outer dynein row

Summary

Introduction

Flagellar dyneins fall into two broad groups: outer row dyneins, which are essential for maintaining normal beat frequency and for some calcium-dependent waveform changes, and inner row dyneins, which are needed for normal waveform and for some tactic responses [10]. Oda7 cells lack any observable pool of outer row dynein heavy chain ␣ (the oda11 gene product), they retain normal levels of other motor subunits [13], suggesting that oda7 interacts in some unique way with this heavy chain.

Results

Conclusion