title: Mass-dependent bond vibrational dynamics influence catalysis by HIV-1 protease.
abstract: Protein motions that occur on the microsecond to millisecond time scale have been linked to enzymatic rates observed for catalytic turnovers, but not to transition-state barrier crossing. It has been hypothesized that enzyme motions on the femtosecond time scale of bond vibrations play a role in transition state formation. Here, we perturb femtosecond motion by substituting all nonexchangeable carbon, nitrogen, and hydrogen atoms with (13)C, (15)N, and (2)H and observe the catalytic effects in HIV-1 protease. According to the Born-Oppenheimer approximation, isotopic substitution alters vibrational frequency with unchanged electrostatic properties. With the use of a fluorescent peptide to report on multiple steps in the reaction, we observe significantly reduced rates in the heavy enzyme relative to the light enzyme. A possible interpretation of our results is that there exists a dynamic link between mass-dependent bond vibrations of the enzyme and events in the reaction coordinate.
authors: Department of Biochemistry, Albert Einstein College of Medicine at Yeshiva University, 1300 Morris Park Avenue, Bronx, New York 10461, USA.
authors: D Randal
authors: DR
authors: Kipp
authors: Rafael G
authors: RG
authors: Silva
authors: Vern L
authors: VL
authors: Schramm
mesh_terms: D002942:Circular Dichroism; D015658:HIV Infections / Q000201:enzymology / Q000821:virology; D016333:HIV Protease / Q000737:chemistry / Q000378:metabolism*; D015497:HIV-1 / Q000201:enzymology*; D007700:Kinetics; D056004:Molecular Dynamics Simulation
chemical_list: D016333:HIV Protease; C514803:p16 protease, Human immunodeficiency virus 1