Transfer of high sensitivity for benzothiazepines from L-type to class A (BI) calcium channels.
To investigate the molecular basis of the calcium channel block by diltiazem, we transferred amino acids of the highly sensitive and stereoselective L-type (alpha1S or alpha1C) to a weakly sensitive, nonstereoselective class A (alpha1A) calcium channel. Transfer of three amino acids of transmembrane segment IVS6 of L-type alpha1 into the alpha1A subunit (I1804Y, S1808A, and M1811I) was sufficient to support a use-dependent block by diltiazem and by the phenylalkylamine (-)-gallopamil after expression in Xenopus oocytes. An additional mutation F1805M increased the sensitivity for (-)-gallopamil but not for diltiazem. Our data suggest that the receptor domains for diltiazem and gallopamil have common but not identical molecular determinants in transmembrane segment IVS6. These mutations also identified single amino acid residues in segment IVS6 that are important for class A channel inactivation.
Hering
S
S
Institut für Biochemische Pharmakologie, University of Innsbruck, Peter Mayr Strasse 1, A-6020 Innsbruck, Austria.
Aczél
S
S
Grabner
M
M
Döring
F
F
Berjukow
S
S
Mitterdorfer
J
J
Sinnegger
M J
MJ
Striessnig
J
J
Degtiar
V E
VE
Wang
Z
Z
Glossmann
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D020746:Calcium Channels, L-Type; D004110:Diltiazem / Q000494:pharmacology*; D005711:Gallopamil / Q000494:pharmacology; D017136:Ion Transport; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D014981:Xenopus
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D001464:Barium; D005711:Gallopamil; D004110:Diltiazem