Linked Life Data

10779517

Source:http://linkedlifedata.com/resource/pubmed/id/10779517

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
28
pubmed:dateCreated
2000-8-16
pubmed:abstractText
L-type Ca(2+) channels are unusual in displaying two opposing forms of autoregulatory feedback, Ca(2+)-dependent inactivation and facilitation. Previous studies suggest that both involve direct interactions between calmodulin (CaM) and a consensus CaM-binding sequence (IQ motif) in the C terminus of the channel's alpha(1C) subunit. Here we report the functional effects of an extensive series of modifications of the IQ motif aimed at dissecting the structural determinants of the different forms of modulation. Although the combined substitution by alanine at five key positions (Ile(1624), Gln(1625), Phe(1628), Arg(1629), and Lys(1630)) abolished all Ca(2+) dependence, corresponding single alanine replacements behaved similarly to the wild-type channel (77wt) in four of five cases. The mutant I1624A stood out in displaying little or no Ca(2+)-dependent inactivation, but clear Ca(2+)- and frequency-dependent facilitation. An even more pronounced tilt in favor of facilitation was seen with the double mutant I1624A/Q1625A: overt facilitation was observed even during a single depolarizing pulse, as confirmed by two-pulse experiments. Replacement of Ile(1624) by 13 other amino acids produced graded and distinct patterns of change in the two forms of modulation. The extent of Ca(2+)-dependent facilitation was monotonically correlated with the affinity of CaM for the mutant IQ motif, determined in peptide binding experiments in vitro. Ca(2+)-dependent inactivation also depended on strong CaM binding to the IQ motif, but showed an additional requirement for a bulky, hydrophobic side chain at position 1624. Abolition of Ca(2+)-dependent modulation by IQ motif modifications mimicked and occluded the effects of overexpressing a dominant-negative CaM mutant.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
14
pubmed:volume
275
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
21121-9
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2000
pubmed:articleTitle
Ca2+-sensitive inactivation and facilitation of L-type Ca2+ channels both depend on specific amino acid residues in a consensus calmodulin-binding motif in the(alpha)1C subunit.
pubmed:affiliation
Department of Pharmacology, University of Bern, 3010 Bern, Switzerland. USA. zuehlke@pki.unibe.ch
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't