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

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

Molecular biology of the cell (2016-03-25)
Hiroshi Qadota, Olga Mayans, Yohei Matsunaga, Jonathan L McMurry, Kristy J Wilson, Grace E Kwon, Rachel Stanford, Kevin Deehan, Tina L Tinley, Verra M Ngwa, Guy M Benian
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Anti-Glutathione-S-Transferase (GST)–Peroxidase Conjugate antibody produced in rabbit, IgG fraction of antiserum, buffered aqueous solution
Sigma-Aldrich
Anti-HA antibody, Mouse monoclonal, clone HA-7, purified from hybridoma cell culture