The SH3 domain of UNC-89 (obscurin) interacts with paramyosin, a coiled-coil protein, in Caenorhabditis elegans muscle

• Type of Material: Article
• Authors: Hiroshi Qadota, Emory University; Olga Mayans, University of Konstanz; Yohei Matsunaga, Emory University; Jonathan L. McMurry, Kennesaw State University; Kristy J. Wilson, Emory University; Grace E. Kwon, Emory University; Rachel Stanford, Emory University; Kevin Deehan, Emory University; Tina L. Tinley, Emory University; Verra M. Ngwa, Kennesaw State University; Guy Benian, Emory University
• Language: English
• Date: 2016-05-15
• Publisher: American Society for Cell Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2016 Qadota et al.
• License: Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1091/mbc.E15-09-0675
• Title of Journal or Parent Work: Molecular Biology of the Cell
• ISSN: 1059-1524
• Volume: 27
• Issue: 10
• Start Page: 1606
• End Page: 1620
• Grant/Funding Information: This study was supported in part by National Institutes of Health Grant R01AR064307 and a pilot grant from Merial Limited to G.M.B.; This study was also supported in part by the Emory Integrated Genomics Core, which is subsidized by the Emory University School of Medicine and is one of the Emory Integrated Core Facilities.
• Keywords: MYOSIN ROD; MUTANTS; Life Sciences & Biomedicine; M-LINES; Science & Technology; THICK FILAMENTS; C-ELEGANS; SMALL ANKYRIN-1; SKELETAL-MUSCLE; KINASE DOMAINS; BODY-WALL MUSCLE; Cell Biology; SARCOPLASMIC-RETICULUM
• Research Categories: Biology, Cell; Health Sciences, Pathology

Abstract

UNC-89 is a giant polypeptide located at the sarcomeric M-line of Caenorhabditis elegans muscle. The human homologue is obscurin. To understand how UNC-89 is localized and functions, we have been identifying its binding partners. Screening a yeast two-hybrid library revealed that UNC-89 interacts with paramyosin. Paramyosin is an invertebrate-specific coiled-coil dimer protein that is homologous to the rod portion of myosin heavy chains and resides in thick filament cores. Minimally, this interaction requires UNC- 89's SH3 domain and residues 294-376 of paramyosin and has a KD of ∼1.1 μM. In unc-89 loss-of-function mutants that lack the SH3 domain, paramyosin is found in accumulations. When the SH3 domain is overexpressed, paramyosin is mislocalized. SH3 domains usually interact with a proline-rich consensus sequence, but the region of paramyosin that interacts with UNC-89's SH3 is α-helical and lacks prolines. Homology modeling of UNC-89's SH3 suggests structural features that might be responsible for this interaction. The SH3-binding region of paramyosin contains a "skip residue," which is likely to locally unwind the coiled-coil and perhaps contributes to the binding specificity.