Neuronal nitric-oxide synthase interaction with calmodulin-troponin C chimeras

被引:55
作者
Gachhui, R
Abu-Soud, HM
Ghoshà, DK
Presta, A
Blazing, MA
Mayer, B
George, SE
Stuehr, DJ
机构
[1] Cleveland Clin Fdn, Res Inst, Dept Immunol, Cleveland, OH 44195 USA
[2] Duke Univ, Med Ctr, Dept Med, Durham, NC 27710 USA
[3] Duke Univ, Med Ctr, Dept Pharmacol, Durham, NC 27710 USA
[4] Karl Franzens Univ Graz, Inst Pharmakol & Toxikol, A-8010 Graz, Austria
关键词
D O I
10.1074/jbc.273.10.5451
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Calmodulin (CaM) binding activates neuronal nitric-oxide synthase (nNOS) catalytic functions and also upregulates electron transfer into its flavin and heme centers, Here, we utilized seven tight binding CaM-troponin C chimeras, which variably activate nNOS NO synthesis to examine the relationship between CaM domain structure, activation of catalytic functions, and control of internal electron transfer at two points within nNOS, Chimeras that were singly substituted with troponin C domains 4, 3, 2, or 1 were increasingly unable to activate NO synthesis, but all caused some activation of cytochrome c reduction compared with CaM-free nNOS, The magnitude by which each chimera activated NO synthesis was approximately proportional to the rate of heme iron reduction supported by each chimera, which varied from 0% to similar to 80% compared with native CaM and remained coupled to NO synthesis in all cases, In contrast, chimera activation of cytochrome c reduction was not always associated with accelerated reduction of nNOS flavins, and certain chimeras activated cytochrome c reduction without triggering heme iron reduction, We conclude: 1) CaM effects on electron transfer at two points within nNOS can be functionally separated. 2) CaM controls NO synthesis by governing heme iron reduction, but enhances reductase activity by two mechanisms, only one of which is associated with an increased rate of flavin reduction.
引用
收藏
页码:5451 / 5454
页数:4
相关论文
共 24 条