title: Structural model for phenylalkylamine binding to L-type calcium channels.
abstract: Phenylalkylamines (PAAs), a major class of L-type calcium channel (LTCC) blockers, have two aromatic rings connected by a flexible chain with a nitrile substituent. Structural aspects of ligand-channel interactions remain unclear. We have built a KvAP-based model of LTCC and used Monte Carlo energy minimizations to dock devapamil, verapamil, gallopamil, and other PAAs. The PAA-LTCC models have the following common features: (i) the meta-methoxy group in ring A, which is proximal to the nitrile group, accepts an H-bond from a PAA-sensing Tyr_IIIS6; (ii) the meta-methoxy group in ring B accepts an H-bond from a PAA-sensing Tyr_IVS6; (iii) the ammonium group is stabilized at the focus of P-helices; and (iv) the nitrile group binds to a Ca(2+) ion coordinated by the selectivity filter glutamates in repeats III and IV. The latter feature can explain Ca(2+) potentiation of PAA action and the presence of an electronegative atom at a similar position of potent PAA analogs. Tyr substitution of a Thr in IIIS5 is known to enhance action of devapamil and verapamil. Our models predict that the para-methoxy group in ring A of devapamil and verapamil accepts an H-bond from this engineered Tyr. The model explains structure-activity relationships of PAAs, effects of LTCC mutations on PAA potency, data on PAA access to LTCC, and Ca(2+) potentiation of PAA action. Common and class-specific aspects of action of PAAs, dihydropyridines, and benzothiazepines are discussed in view of the repeat interface concept.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.
authors.forename: Ricky C K
authors.initials: RCK
authors.lastname: Cheng
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada; Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg 194223, Russia.
authors.forename: Denis B
authors.initials: DB
authors.lastname: Tikhonov
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada. Electronic address: zhorov@mcmaster.ca.
authors.forename: Boris S
authors.initials: BS
authors.lastname: Zhorov
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002121:Calcium Channel Blockers / Q000737:chemistry / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D003198:Computer Simulation; D004095:Dihydropyridines / Q000737:chemistry; D005711:Gallopamil / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009010:Monte Carlo Method; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D014700:Verapamil / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; D005711:Gallopamil; D014700:Verapamil; C055885:devapamil
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