NMR Assignment and Secondary Structure of Coiled Coil Domain of C-terminal Myosin Binding Subunit of Myosin Phosphatase

Protein-protein interactions between the C-terminal domain of Myosin Binding Subunit (MBS) of MLC Phosphatase (MBSCT180; C-terminal 180 aa) and the N-terminal coiled coil (CC) leucine zipper (LZ) domain of PKGI α, PKG-Iα1-159 play an important role in the process of Smooth Muscle Cell relaxation. The paucity of three-dimensional structural information for MBSCT180 prevents an atomic level understanding of the MBS–PKG contractile complex. MBSCT180 is comprised of three structurally different sub-domains including a non-canonical CC, a CC, and a LZ. Recently we reported polypeptide purification and biophysical characterization of the CC domain and the LZ domain of MBSCT180 (Sharma et al, Prot Expr Purif 2012). Here we report 1H, 13C, 15N chemical shift assignments of homodimeric CC MBS domain encompassing amino acid residues Asp931-Leu980 using 2D and 3D heteronuclear NMR spectroscopy. Secondary structure analyses deduced from these NMR chemical shift data have identified a contiguous stretch of 36 residues from Phe932 to Ala967 that is involved in the formation of coiled coil α-helical region within CC MBS domain. The N-terminal residue Asp931 and the C-terminally positioned residues Thr968-Ala975, Arg977, and Ser978 adopt nonhelical loop conformations.