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Sharma AK, Birrane G, Anklin C, Rigby AC, Alper SL. NMR insight into myosin-binding subunit coiled-coil structure reveals binding interface with protein kinase G-Iα leucine zipper in vascular function. J Biol Chem 2017; 292:7052-7065. [PMID: 28280239 DOI: 10.1074/jbc.m117.781260] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 03/08/2017] [Indexed: 11/06/2022] Open
Abstract
Nitrovasodilators relax vascular smooth-muscle cells in part by modulating the interaction of the C-terminal coiled-coil domain (CC) and/or the leucine zipper (LZ) domain of the myosin light-chain phosphatase component, myosin-binding subunit (MBS), with the N-terminal LZ domain of protein kinase G (PKG)-Iα. Despite the importance of vasodilation in cardiovascular homeostasis and therapy, our structural understanding of the MBS CC interaction with LZ PKG-1α has remained limited. Here, we report the 3D NMR solution structure of homodimeric CC MBS in which amino acids 932-967 form a coiled-coil of two monomeric α-helices in parallel orientation. We found that the structure is stabilized by non-covalent interactions, with dominant contributions from hydrophobic residues at a and d heptad positions. Using NMR chemical-shift perturbation (CSP) analysis, we identified a subset of hydrophobic and charged residues of CC MBS (localized within and adjacent to the C-terminal region) contributing to the dimer-dimer interaction interface between homodimeric CC MBS and homodimeric LZ PKG-Iα. 15N backbone relaxation NMR revealed the dynamic features of the CC MBS interface residues identified by NMR CSP. Paramagnetic relaxation enhancement- and CSP-NMR-guided HADDOCK modeling of the dimer-dimer interface of the heterotetrameric complex exhibits the involvement of non-covalent intermolecular interactions that are localized within and adjacent to the C-terminal regions of each homodimer. These results deepen our understanding of the binding restraints of this CC MBS·LZ PKG-Iα low-affinity heterotetrameric complex and allow reevaluation of the role(s) of myosin light-chain phosphatase partner polypeptides in regulation of vascular smooth-muscle cell contractility.
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Affiliation(s)
- Alok K Sharma
- From the Division of Nephrology and Center for Vascular Biology Research, .,the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215
| | - Gabriel Birrane
- the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215.,Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Clemens Anklin
- Bruker Biospin Corp., Billerica, Massachusetts 01821, and
| | - Alan C Rigby
- Warp Drive Bio, Inc., Cambridge, Massachusetts 02139
| | - Seth L Alper
- From the Division of Nephrology and Center for Vascular Biology Research, .,the Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215
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Sharma AK, Friedman DJ, Pollak MR, Alper SL. Structural characterization of the C-terminal coiled-coil domains of wild-type and kidney disease-associated mutants of apolipoprotein L1. FEBS J 2016; 283:1846-62. [PMID: 26945671 DOI: 10.1111/febs.13706] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Revised: 01/25/2016] [Accepted: 03/02/2016] [Indexed: 01/08/2023]
Abstract
Trypanosomes that cause sleeping sickness endocytose apolipoprotein L1 (APOL1)-containing trypanolytic factors from human serum, leading to trypanolytic death through generation of APOL1-associated lytic pores in trypanosomal membranes. The trypanosome Trypanosoma brucei rhodesiense counteracts trypanolysis by expressing the surface protein serum response-associated (SRA), which can bind APOL1 common variant G0 to block its trypanolytic activity. However, two missense variants in the C terminal predicted coiled-coil (CC) domains of human APOL1 G1 (S342G/I384M) and G2 (ΔN388Y389) decrease or abrogate APOL1 binding to T. brucei rhodesiense SRA, thus preserving APOL1 trypanolytic activity. These evolutionarily selected APOL1 missense variants, found at a high frequency in some populations of African descent, also confer elevated risk of kidney disease. Understanding the SRA-APOL1 interaction and the role of APOL1 G1 and G2 variants in kidney disease demands structural characterization of the APOL1 CC domain. Using CD, heteronuclear NMR, and molecular dynamics (MD) simulation on structural homology models, we report here unique and dynamic solution conformations of nephropathy variants G1 and G2 as compared with the common variant G0. Conformational plasticity in G1 and G2 CC domains led to interhelical α1-α2 approximation coupled with secondary structural changes and delimited motional properties absent in the G0 CC domain. The G1 substitutions conferred local structural changes principally along helix α1, whereas the G2 deletion altered the structure of both helix α2 and helix α1. These dynamic features of APOL1 CC variants likely reflect their intrinsic structural properties, and should help interpret future APOL1 structural studies and define the contribution of APOL1 risk variants to kidney disease.
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Affiliation(s)
- Alok K Sharma
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - David J Friedman
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Martin R Pollak
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
| | - Seth L Alper
- Nephrology Division, Harvard Medical School, Boston, MA, USA.,Center for Vascular Biology Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.,Department of Medicine, Harvard Medical School, Boston, MA, USA
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