Unfair competition governs the interaction of pCPI-17 with myosin phosphatase (PP1-MYPT1)
Abstract
The small phosphoprotein pCPI-17 inhibits myosin light chain phosphatase (MLCP). Current models postulate that during muscle relaxation, phosphatases other than MLCP dephosphorylate and inactivate pCPI-17 to restore MLCP activity. We show here that such hypotheses are insufficient to account for the observed rapidity of pCPI-17 inactivation in mammalian smooth muscles. Instead, MCLP itself is the critical enzyme for pCPI-17 dephosphorylation. We call the mutual sequestration mechanism through which pCPI-17 and MLCP interact inhibition by unfair competition: MLCP protects pCPI-17 from other phosphatases, while pCPI-17 blocks other substrates from MLCP's active site. MLCP dephosphorylates pCPI-17 at a slow rate that is nonetheless both sufficient and necessary to explain the speed of pCPI-17 dephosphorylation and the consequent MLCP activation during muscle relaxation.
Article and author information
Author details
Funding
NIH Office of the Director (GM048430)
- Michael L Goldberg
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Roger J Davis, University of Massachusetts Medical School, United States
Version history
- Received: December 24, 2016
- Accepted: March 31, 2017
- Accepted Manuscript published: April 7, 2017 (version 1)
- Accepted Manuscript updated: April 12, 2017 (version 2)
- Accepted Manuscript updated: April 20, 2017 (version 3)
- Version of Record published: May 23, 2017 (version 4)
Copyright
© 2017, Filter et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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