Proteomic characterization of sperm radial spokes identifies a novel spoke protein with an ubiquitin domain

Radial spokes are T-shaped protein complexes important for the regulation of axonemal dyneins in eukaryotic cilia and flagella. Using a functional proteomics approach, we identified six spoke proteins in spermagella of the ascidian Ciona intestinalis. Many of the domain/motif structures in spoke proteins are commonly found in flagella of both Ciona sperm and Chlamydomonas, but interestingly they often distribute over non-orthologous protein components. A novel 116 kDa protein named CMUB116 has both an ubiquitin domain and an IQ motif. It has orthologs in vertebrates, but not in Chlamydomonas. Furthermore, the results obtained by immunological analysis provide strong indication that CMUB116 is located at the stalk of radial spokes, where it is associated with MORN40. Structured summary: MINT-7148244: CMUB116 (genbank_protein_gi: BAH59277) and MORN40 (genbank_protein_gi: BAH59284) colocalize (MI: 0403) by cosedimentation (MI: 0027) MINT-7148179: Ci-RSP3 (uniprotkb: Q8T898) physically interacts (MI: 0915) with tubulin alpha (uniprotkb: Q8MVT7), LRR37 (uniprotkb: Q8T896), CMUB116 (genbank_protein_gi: BAH59277), Ci-SRP4/6 (genbank_protein_gi: BAH59283), AK58 (genbank_protein_gi: BAM59278), tubulin beta (genbank_protein_ gi: XP_002130315), NDK/DPY26 (genbank_protein_ gi: BAH59279), MORN40 (genbank_protein_ gi: BAH 59284), ARM37 (genbank_protein_ gi: BAH59280), NDK/DPY26 (genbank_protein_ gi: NP_001161489), LC8 (genbank_protein_ gi: BAH59282) and Ci-RSP9 (genbank_protein_ gi: NP_001154962) by anti bait coimmunoprecipitation (MI: 0006) MINT-7148272: Ci-RSP3 (uniprotkb: Q8T898) and MORN40 (genbank_protein_ gi: BAH59284) colocalize (MI: 0403) by cosedimentation (MI: 0027) (C) 2009 Federation of European Biochemical Societies. Published by Elsevier B. V. All rights reserved.