TY - JOUR
T1 - Investigating a back door mechanism of actin phosphate release by steered molecular dynamics
AU - Wriggers, Willy
AU - Schulten, Klaus
PY - 1999/5/1
Y1 - 1999/5/1
N2 - In actin-based cell motility, phosphate P(i) release after ATP hydrolysis is an essential biochemical process, but the actual pathway of P(i) separation from actin is not well understood. We report a series of molecular dynamics simulations that induce the dissociation of P(i) from actin. After cleavage from ATP, the singly protonated phosphate (HPO42-) rotates about the ADP-associated Ca2+ ion, turning away from the negatively charged ADP towards the putative exit near His73. To reveal the microscopic processes underlying the release of P(i), adhesion forces were measured when pulling the substrate out of its binding pocket. The results suggest that the separation from the divalent cation is the rate-limiting step in P(i) release. Protonation of HPO42- to H2PO4- lowers the electrostatic barrier during P(i) liberation from the ion. The simulations revealed a propensity of charged His73+ to form a salt bridge with HPO42-, but not with H2PO4-. His73 stabilizes HPO42- and, thereby, inhibits rapid P(i) release from actin. Arg177 remains attached to P(i) along the putative back door pathway, suggesting a shuttle function that facilitates the transport of P(i) to a binding site on the protein surface.
AB - In actin-based cell motility, phosphate P(i) release after ATP hydrolysis is an essential biochemical process, but the actual pathway of P(i) separation from actin is not well understood. We report a series of molecular dynamics simulations that induce the dissociation of P(i) from actin. After cleavage from ATP, the singly protonated phosphate (HPO42-) rotates about the ADP-associated Ca2+ ion, turning away from the negatively charged ADP towards the putative exit near His73. To reveal the microscopic processes underlying the release of P(i), adhesion forces were measured when pulling the substrate out of its binding pocket. The results suggest that the separation from the divalent cation is the rate-limiting step in P(i) release. Protonation of HPO42- to H2PO4- lowers the electrostatic barrier during P(i) liberation from the ion. The simulations revealed a propensity of charged His73+ to form a salt bridge with HPO42-, but not with H2PO4-. His73 stabilizes HPO42- and, thereby, inhibits rapid P(i) release from actin. Arg177 remains attached to P(i) along the putative back door pathway, suggesting a shuttle function that facilitates the transport of P(i) to a binding site on the protein surface.
KW - Actin function
KW - ATP hydrolysis
KW - Divalent cation
KW - Non- equilibrium molecular dynamics
KW - Phosphate titration
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U2 - 10.1002/(SICI)1097-0134(19990501)35:2<262::AID-PROT11>3.0.CO;2-N
DO - 10.1002/(SICI)1097-0134(19990501)35:2<262::AID-PROT11>3.0.CO;2-N
M3 - Article
C2 - 10223297
AN - SCOPUS:0033136019
SN - 0887-3585
VL - 35
SP - 262
EP - 273
JO - Proteins: Structure, Function and Genetics
JF - Proteins: Structure, Function and Genetics
IS - 2
ER -