Linked Life Data

9100027

Source:http://linkedlifedata.com/resource/pubmed/id/9100027

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
14
pubmed:dateCreated
1997-5-15
pubmed:abstractText
The binding of Mg2+ to calmodulin (CaM) and the effect of Mg2+ on the binding of Ca2+-CaM to target peptides were examined using two-dimensional nuclear magnetic resonance and fluorescence spectroscopic techniques. We found that Mg2+ preferentially binds to Ca2+-binding sites I and IV of CaM in the absence of Ca2+ and that Ca2+-binding site III displays the lowest affinity for Mg2+. In contrast to the marked structural transitions induced by Ca2+ binding, Mg2+ binding causes only localized conformational changes within the four Ca2+-binding loops of CaM. Therefore, Mg2+ does not seem to be able to cause significant structural effects required for the interaction of CaM with target proteins. The presence of excess Mg2+ (up to 10 mM) does not change the order and cooperativity of Ca2+ binding to CaM, and as expected, the structure of Ca2+-saturated CaM is not affected by the presence of Mg2+. However, we found that the binding of Ca2+-saturated CaM to target peptides is affected by Mg2+ with the binding affinity decreasing as the Mg2+ concentration increases. Three different peptides, corresponding to the CaM binding domain of skeletal muscle myosin light-chain kinase (MLCK), CaM-dependent cyclic nucleotide phosphodiesterase (PDE), and smooth muscle caldesmon (CaD), were examined and show different reductions in their affinities toward CaM. The CaM-binding affinity of the MLCK peptide in the presence of 50 mM Mg2+ is approximately 40-fold lower than that seen in the absence of Mg2+, and a similar response was observed for the PDE peptide. The affinity of the CaD peptide for CaM also shows a Mg2+ dependence, though to a much lower magnitude. The Mg2+-dependent decrease in the affinities between CaM and its target peptides is an intrinsic property of Mg2+ rather than a nonspecific ionic effect, as other metal ions such as Na+ do not completely replicate the effect of Mg2+. The inhibitory effect of Mg2+ on the formation of complexes between CaM and its targets may contribute to the specificity of CaM in target activation in response to cellular Ca2+ concentration fluctuations.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
8
pubmed:volume
36
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4309-16
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1997
pubmed:articleTitle
Identification of Mg2+-binding sites and the role of Mg2+ on target recognition by calmodulin.
pubmed:affiliation
Department of Biochemistry, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't