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Jiang T, Wan G, Zhang H, Gyawali YP, Underbakke ES, Feng C. Mapping the Intersubunit Interdomain FMN-Heme Interactions in Neuronal Nitric Oxide Synthase by Targeted Quantitative Cross-Linking Mass Spectrometry. Biochemistry 2024; 63:1395-1411. [PMID: 38747545 DOI: 10.1021/acs.biochem.4c00157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Nitric oxide synthase (NOS) in mammals is a family of multidomain proteins in which interdomain electron transfer (IET) is controlled by domain-domain interactions. Calmodulin (CaM) binds to the canonical CaM-binding site in the linker region between the FMN and heme domains of NOS and allows tethered FMN domain motions, enabling an intersubunit FMN-heme IET in the output state for NO production. Our previous cross-linking mass spectrometric (XL MS) results demonstrated site-specific protein dynamics in the CaM-responsive regions of rat neuronal NOS (nNOS) reductase construct, a monomeric protein [Jiang et al., Biochemistry, 2023, 62, 2232-2237]. In this work, we have extended our combined approach of XL MS structural mapping and AlphaFold structural prediction to examine the homodimeric nNOS oxygenase/FMN (oxyFMN) construct, an established model of the NOS output state. We employed parallel reaction monitoring (PRM) based quantitative XL MS (qXL MS) to assess the CaM-induced changes in interdomain dynamics and interactions. Intersubunit cross-links were identified by mapping the cross-links onto top AlphaFold structural models, which was complemented by comparing their relative abundances in the cross-linked dimeric and monomeric bands. Furthermore, contrasting the CaM-free and CaM-bound nNOS samples shows that CaM enables the formation of the intersubunit FMN-heme docking complex and that CaM binding induces extensive, allosteric conformational changes across the NOS regions. Moreover, the observed cross-links sites specifically respond to changes in ionic strength. This indicates that interdomain salt bridges are responsible for stabilizing and orienting the output state for efficient FMN-heme IET. Taken together, our targeted qXL MS results have revealed that CaM and ionic strength modulate specific dynamic changes in the CaM/FMN/heme complexes, particularly in the context of intersubunit interdomain FMN-heme interactions.
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Affiliation(s)
- Ting Jiang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Guanghua Wan
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Haikun Zhang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Yadav Prasad Gyawali
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Eric S Underbakke
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011, United States
| | - Changjian Feng
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States
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Singh S, Gyawali YP, Jiang T, Bukowski GS, Zheng H, Zhang H, Owopetu R, Thielges MC, Feng C. Probing calmodulin-NO synthase interactions via site-specific infrared spectroscopy: an introductory investigation. J Biol Inorg Chem 2024; 29:243-250. [PMID: 38580821 PMCID: PMC11181464 DOI: 10.1007/s00775-024-02046-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 01/15/2024] [Indexed: 04/07/2024]
Abstract
Calmodulin (CaM) binds to a linker between the oxygenase and reductase domains of nitric oxide synthase (NOS) to regulate the functional conformational dynamics. Specific residues on the interdomain interface guide the domain-domain docking to facilitate the electron transfer in NOS. Notably, the docking interface between CaM and the heme-containing oxygenase domain of NOS is isoform specific, which is only beginning to be investigated. Toward advancing understanding of the distinct CaM-NOS docking interactions by infrared spectroscopy, we introduced a cyano-group as frequency-resolved vibrational probe into CaM individually and when associated with full-length and a bi-domain oxygenase/FMN construct of the inducible NOS isoform (iNOS). Site-specific, selective labeling with p-cyano-L-phenylalanine (CNF) by amber suppression of CaM bound to the iNOS has been accomplished by protein coexpression due to the instability of recombinant iNOS protein alone. We introduced CNF at residue 108, which is at the putative CaM-heme (NOS) docking interface. CNF was also introduced at residue 29, which is distant from the docking interface. FT IR data show that the 108 site is sensitive to CaM-NOS complex formation, while insensitivity to its association with the iNOS protein or peptide was observed for the 29 site. Moreover, narrowing of the IR bands at residue 108 suggests the C≡N probe experiences a more limited distribution of environments, indicating side chain restriction apparent for the complex with iNOS. This initial work sets the stage for residue-specific characterizations of structural dynamics of the docked states of NOS proteins.
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Affiliation(s)
- Swapnil Singh
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
| | - Yadav Prasad Gyawali
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Ting Jiang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Gregory S Bukowski
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
| | - Huayu Zheng
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Haikun Zhang
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Rebecca Owopetu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Megan C Thielges
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA.
| | - Changjian Feng
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA.
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, 87131, USA.
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Zheng H, Li J, Feng C. An isoform-specific pivot modulates the electron transfer between the flavin mononucleotide and heme centers in inducible nitric oxide synthase. J Biol Inorg Chem 2020; 25:1097-1105. [PMID: 33057871 PMCID: PMC7669679 DOI: 10.1007/s00775-020-01824-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Accepted: 09/24/2020] [Indexed: 11/25/2022]
Abstract
Intraprotein interdomain electron transfer (IET) between the flavin mononucleotide (FMN) and heme centers is an obligatory step in nitric oxide synthase (NOS) enzymes. An isoform-specific pivotal region near Leu406 in the heme domain of human inducible NOS (iNOS) was proposed to mediate the FMN-heme domain-domain alignment (J Inorg Biochem 153:186-196, 2015). The FMN-heme IET rate is a measure of the interdomain FMN/heme complex formation. In this work, the FMN-heme IET kinetics in the wild type (wt) human iNOS oxygenase/FMN (oxyFMN) construct were directly measured by laser flash photolysis with added synthetic peptide related to the pivotal region, in comparison with the wt construct alone. The IET rates were decreased by the iNOS HKL peptide in a dose-saturable fashion, and the inhibitory effect was abolished by a single L406 → E mutation in the peptide. A similar trend in change of the NO synthesis activity of wt iNOS holoenzyme by the peptides was observed. These data, along with the kinetics and modeling results for the L406T and L406F mutant oxyFMN proteins, indicated that the Leu406 residue modulates the FMN-heme IET through hydrophobic interactions. Moreover, the IET rates were analyzed for the wt iNOS oxyFMN protein in the presence of nNOS or eNOS-derived peptide related to the equivalent pivotal heme domain site. These results together indicate that the isoform-specific pivotal region at the heme domain specifically interacts with the conserved FMN domain surface, to facilitate proper interdomain docking for the FMN-heme IET in NOS.
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Affiliation(s)
- Huayu Zheng
- College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Jinghui Li
- College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Changjian Feng
- College of Pharmacy, University of New Mexico, Albuquerque, NM, 87131, USA.
- Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, 87131, USA.
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Zheng H, Li J, Feng C. Heat shock protein 90 enhances the electron transfer between the FMN and heme cofactors in neuronal nitric oxide synthase. FEBS Lett 2020; 594:2904-2913. [PMID: 32573772 DOI: 10.1002/1873-3468.13870] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 05/30/2020] [Accepted: 06/04/2020] [Indexed: 11/05/2022]
Abstract
Heat shock protein 90 (Hsp90) is a key regulator of nitric oxide synthase (NOS) in vivo. Despite its functional importance, little is known about the underlying molecular mechanism. Here, purified dimeric human Hsp90α was used to investigate whether (and if so, how) Hsp90 affects the FMN-heme interdomain electron transfer (IET) step in NOS. Hsp90α increases the IET rate for rat neuronal NOS (nNOS) in a dose-saturable manner, and a single charge-neutralization mutation at conserved Hsp90 K585 abolishes the effect. The kinetic results with added Ficoll 70, a crowder, further indicate that Hsp90 enhances the FMN-heme IET through specific association with nNOS. The Hsp90-nNOS docking models provide hints on the putative role of Hsp90 in constraining the available conformational space for the FMN domain motions.
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Affiliation(s)
- Huayu Zheng
- College of Pharmacy, University of New Mexico, Albuquerque, NM, USA.,Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA
| | - Jinghui Li
- College of Pharmacy, University of New Mexico, Albuquerque, NM, USA
| | - Changjian Feng
- College of Pharmacy, University of New Mexico, Albuquerque, NM, USA.,Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, NM, USA
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Generation and characterization of functional phosphoserine-incorporated neuronal nitric oxide synthase holoenzyme. J Biol Inorg Chem 2018; 24:1-9. [PMID: 30315355 DOI: 10.1007/s00775-018-1621-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Accepted: 10/05/2018] [Indexed: 12/19/2022]
Abstract
Phosphorylation is an important pathway for the regulation of nitric oxide synthase (NOS) at the posttranslational level. However, the molecular underpinnings of NOS regulation by phosphorylations remain unclear to date, mainly because of the problems in making a good amount of active phospho-NOS proteins. Herein, we have established a system in which recombinant rat nNOS holoprotein can be produced with site-specific incorporation of phosphoserine (pSer) at residue 1412, using a specialized bacterial host strain for pSer incorporation. The pSer1412 nNOS protein demonstrates UV-Vis, far-UV CD and fluorescence spectral properties that are identical to those of nNOS overexpressed in other bacterial strains. The protein is also functional, possessing normal NO production and NADPH oxidation activities in the presence of abundant substrate L-Arg. Conversely, the rate of FMN-heme interdomain electron transfer (IET) in pSer1412 nNOS is considerably lower than that of wild-type (wt) nNOS, while the phosphomimetic S1142E mutant possesses similar electron transfer kinetics to that of wt. The successful incorporation and high yield of pSer1412 into rat nNOS and the significant change in the IET kinetics upon the phosphorylation demonstrate a highly useful method for incorporating native phosphorylation sites as a substantial improvement to commonly used phosphomimetics.
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