Faculty Collaboration Database

Flagellar radial spoke protein 2 is a calmodulin binding protein required for motility in Chlamydomonas reinhardtii. Eukaryot Cell 2004 Feb;3(1):72-81

Date

02/12/2004

Pubmed ID

14871938

Pubmed Central ID

PMC329519

DOI

10.1128/EC.3.1.72-81.2004

Scopus ID

2-s2.0-1242345201 (requires institutional sign-in at Scopus site)   51 Citations

Abstract

Genetic and morphological studies have revealed that the radial spokes regulate ciliary and flagellar bending. Functional and biochemical analysis and the discovery of calmodulin in the radial spokes suggest that the regulatory mechanism involves control of axonemal protein phosphorylation and calcium binding to spoke proteins. To identify potential regulatory proteins in the radial spoke, in-gel kinase assays were performed on isolated axonemes and radial spoke fractions. The results indicated that radial spoke protein 2 (RSP2) can bind ATP and transfer phosphate in vitro. RSP2 was cloned and mapped to the PF24 locus, a gene required for motility. Sequencing revealed that pf24 contains a point mutation converting the first ATG to ATA, resulting in only trace amounts of RSP2 and confirming the RSP2 mapping. Surprisingly, the sequence does not include signature domains for conventional kinases, indicating that RSP2 may not perform as a protein kinase in vivo. However, the predicted RSP2 protein sequence contains Ca2+-dependent calmodulin binding motifs and a GAF domain, a domain found in diverse signaling proteins for binding small ligands including cyclic nucleotides. As predicted from the sequence, recombinant RSP2 binds calmodulin in a calcium-dependent manner. We postulate that RSP2 is a regulatory subunit of the radial spoke involved in localization of calmodulin for control of motility.

Author List

Yang P, Yang C, Sale WS

Author

Pinfen Yang PhD Associate professor in the Biological Sciences department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adenosine Triphosphate
Amino Acid Motifs
Amino Acid Sequence
Animals
Blotting, Western
Calcium
Calmodulin
Calmodulin-Binding Proteins
Chlamydomonas reinhardtii
Chromosome Mapping
Cloning, Molecular
Cyclic AMP
DNA, Complementary
Flagella
Ligands
Models, Biological
Molecular Sequence Data
Movement
Phosphorylation
Plant Proteins
Protein Binding
Protein Isoforms
Protein Structure, Tertiary
Protozoan Proteins
Recombinant Proteins
Sequence Homology, Amino Acid
Signal Transduction
Structure-Activity Relationship