Physiologic relaxation of vascular smooth muscle is induced by the cyclic guanosine monophosphate (cGMP)- dependent protein kinase Iα enzyme (cGKIα), which activates myosin phosphatase (MLCP). This activation process is thought to occur through the interaction involving both
N- and C-terminal leucine zipper coiled-coil (LZCC) domains of the kinase enzyme (cGKIα) with the myosin binding subunit (MBS) of MLCP. In this review, I summarize how to define the LZCC domains in both N-terminal cGKIα1-59and C-terminal MBS proteins using predictive and experimental
methods, how to make a rapid and accurate structure determination of a cGKIα1-59 molecule using NMR's residual dipolar coupling (RDC) measurements, and how to indentify the existence of a weak protein interaction between N-terminal LZCC domain (cGKIα1-59) and a LZCC domain (MBSCT42)
within the C-terminal MBS. In addition, the location and orientation of the residues in LZCC proteins can be readily visualized using a novel diagram, the so-called “wenxiang diagram”, which is more advantageous than traditional helical wheel diagrams in analyzing LZCC protein
structures and their action mechanisms. Using the composed wenxiang diagrams, we have characterized the interaction between cGKIα1- 59 and another LZCC molecule (MBSCT42), and deduced that the most affected residues of these two LZCC molecules might be at the positions d, a, e and g. These
studies and findings are also covered in this review. It is intriguing to see that the successful incorporation of wenxiang diagrams and NMR spectroscopy in the LZCC structural and functional studies may provide some insights into protein-protein interaction mechanisms.
Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.