A study of the molecular mechanism of binding kinetics and long residence times of human CCR5 receptor small molecule allosteric ligands.
BACKGROUND AND PURPOSE
The human CCR5 receptor is a co-receptor for HIV-1 infection and a target for anti-viral therapy. A greater understanding of the binding kinetics of small molecule allosteric ligand interactions with CCR5 will lead to a better understanding of the binding process and may help discover new molecules that avoid resistance.


EXPERIMENTAL APPROACH
Using [(3) H] maraviroc as a radioligand, a number of different binding protocols were employed in conjunction with simulations to determine rate constants, kinetic mechanism and mutant kinetic fingerprints for wild-type and mutant human CCR5 with maraviroc, aplaviroc and vicriviroc.


KEY RESULTS
Kinetic characterization of maraviroc binding to the wild-type CCR5 was consistent with a two-step kinetic mechanism that involved an initial receptor-ligand complex (RA), which transitioned to a more stable complex, R'A, with at least a 13-fold increase in affinity. The dissociation rate from R'A, k-2 , was 1.2 × 10(-3) min(-1) . The maraviroc time-dependent transition was influenced by F85L, W86A, Y108A, I198A and Y251A mutations of CCR5.


CONCLUSIONS AND IMPLICATIONS
The interaction between maraviroc and CCR5 proceeded according to a multi-step kinetic mechanism, whereby initial mass action binding and later reorganizations of the initial maraviroc-receptor complex lead to a complex with longer residence time. Site-directed mutagenesis identified a kinetic fingerprint of residues that affected the binding kinetics, leading to the conclusion that allosteric ligand binding to CCR5 involved the rearrangement of the binding site in a manner specific to each allosteric ligand.
['Swinney|David C|DC|', 'Beavis|Paul|P|', 'Chuang|Kai-Ting|KT|', 'Zheng|Yue|Y|', 'Lee|Ina|I|', 'Gee|Peter|P|', 'Deval|Jerome|J|', 'Rotstein|David M|DM|', 'Dioszegi|Marianna|M|', 'Ravendran|Palani|P|', 'Zhang|Jun|J|', 'Sankuratri|Surya|S|', 'Kondru|Rama|R|', 'Vauquelin|Georges|G|']
D000494:Allosteric Regulation D001665:Binding Sites D065100:CCR5 Receptor Antagonists D003510:Cyclohexanes D004305:Dose-Response Relationship, Drug D006801:Humans D007700:Kinetics D008024:Ligands D000077592:Maraviroc D019713:Receptors, CCR5 D013329:Structure-Activity Relationship D013997:Time Factors D014230:Triazoles
binding kinetics CCR5 allosteric HIV-1 infection maraviroc molecular mechanism of action pharmacology