NDLI: The mechanism of Ca2+ regulation of vascular smooth muscle thin filaments by caldesmon and calmodulin.

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The mechanism of Ca2+ regulation of vascular smooth muscle thin filaments by caldesmon and calmodulin.

Content Provider	Semantic Scholar
Author	Smith, Christopher W. Pritchard, Kevin H. Marston, Steven B.
Copyright Year	1987
Abstract	The interactions of vascular smooth muscle caldesmon with actin, tropomyosin, and calmodulin were determined under conditions in which the four proteins can form reconstituted Ca2+-sensitive smooth muscle thin filaments. Caldesmon bound to actin in a complex fashion with high affinity sites (K = 10(7) M-1) saturating at a stoichiometry of 1 per 28 actins, and lower affinity sites at 1 per 7 actins. The affinity of binding was increased in the presence of tropomyosin, and this could be attributed to a direct interaction between caldesmon and tropomyosin which was demonstrated using caldesmon cross-linked to Sepharose. In the presence of tropomyosin, occupancy of the high affinity sites was associated with inhibition of actin-activated myosin MgATPase activity. Caldesmon was found to bind to calmodulin in the presence of Ca2+, with an affinity of 10(6) M-1. The binding of Ca2+ X calmodulin to caldesmon was associated with the neutralization of inhibition of actin-tropomyosin. Ca2+ X calmodulin binding reduced but did not abolish the binding of caldesmon to actin-tropomyosin. From this data we have proposed a model for smooth muscle thin filaments in which Ca2+ regulates activity by converting the inhibited actin-tropomyosin-caldesmon complex to the active complexes, actin-tropomyosin-caldesmon-calmodulin X Ca2+ and actin-tropomyosin.
File Format	PDF HTM / HTML
PubMed reference number	2947901
Journal	Medline
Volume Number	262
Issue Number	1
Alternate Webpage(s)	http://www.jbc.org/content/262/1/116.full.pdf
Journal	The Journal of biological chemistry
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article

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