Journal
JOURNAL OF MOLECULAR BIOLOGY
Volume 373, Issue 5, Pages 1198-1212Publisher
ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2007.08.049
Keywords
smooth muscle; myosin phosphatase; protein kinase G; analytical ultracentrifugation; surface plasmon resonance
Categories
Funding
- NIAMS NIH HHS [P01 AR41637, R01 AR049066, R01 AR049066-05, R01 AR49066, P01 AR041637, P01 AR041637-110004] Funding Source: Medline
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Nitric oxide induces vasodilation by elevating the production of cGMP, an activator of cGMP-dependent protein kinase (PKG). PKG subsequently causes smooth muscle relaxation in part via activation of myosin light chain phosphatase (MLCP). To date, the interaction between PKG and the targeting subunit of MLCP (MYPT1) is not fully understood. Earlier studies by one group of workers showed that the binding of PKG to MYPT1 is mediated by the leucine-zipper motifs at the N and C termini, respectively, of the two proteins. Another group, however, reported that binding of PKG to MYPT1 did not require the leucine-zipper motif of MYPT1. In this work we fully characterized the interaction between PKG and MYPT1 using biophysical techniques. For this purpose we constructed a recombinant PKG peptide corresponding to a predicted coiled coil region that contains the leucine-zipper motif. We further constructed various C-terminal MYPT1 peptides bearing various combinations of a predicted coiled coil region, extensions preceding this coiled coil region, and the leucine-zipper motif. Our results show, firstly, that while the leucine-zipper motif at the N terminus of PKG forms a homodimeric coiled coil, the one at the C terminus of MYPT1 is monomeric and non-helical. Secondly, the leucine-zipper motif of PKG binds to that of MYPT1 to form a heterodimer. Thirdly, when the zipper motif of MYPT1 is absent, the PKG leucine-zipper motif binds to the coiled coil region and upstream segments of MYPT1 via formation of a heterotetramer. These results provide rationalization of some of the findings by others using alternative binding analyses. (C) 2007 Elsevier Ltd. All rights reserved.
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