Linked Life Data

9096063

Source:http://linkedlifedata.com/resource/pubmed/id/9096063

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1997-6-12
pubmed:abstractText
The gating of ryanodine receptor calcium release channels (RyRs) depends on myoplasmic Ca2+ and Mg2+ concentrations. RyRs from skeletal and cardiac muscle are activated by microm Ca2+ and inhibited by mm Ca2+ and Mg2+. 45Ca2+ release from skeletal SR vesicles suggests two mechanisms for Mg2+-inhibition (Meissner, Darling & Eveleth, 1986, Biochemistry 25:236-244). The present study investigates the nature of these mechanisms using measurements of single-channel activity from cardiac- and skeletal RyRs incorporated into planar lipid bilayers. Our measurements of Mg2+- and Ca2+-dependent gating kinetics confirm that there are two mechanisms for Mg2+ inhibition (Type I and II inhibition) in skeletal and cardiac RyRs. The mechanisms operate concurrently, are independent and are associated with different parts of the channel protein. Mg2+ reduces Po by competing with Ca2+ for the activation site (Type-I) or binding to more than one, and probably two low affinity inhibition sites which do not discriminate between Ca2+ and Mg2+ (Type-II). The relative contributions of the two inhibition mechanisms to the total Mg2+ effect depend on cytoplasmic [Ca2+] in such a way that Mg2+ inhibition has the properties of Types-I and II inhibition at low and high [Ca2+] respectively. Both mechanisms are equally important when [Ca2+] = 10 microm in cardiac RyRs or 1 microm in skeletal RyRs. We show that Type-I inhibition is not the sole mechanism responsible for Mg2+ inhibition, as is often assumed, and we discuss the physiological implications of this finding.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0022-2631
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
156
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
213-29
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Magnesium inhibition of ryanodine-receptor calcium channels: evidence for two independent mechanisms.
pubmed:affiliation
Muscle Research Group, Division of Neuroscience, John Curtin School of Medical Research, Australian National University, GPO Box 334, Canberra, ACT 2601, Australia.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't