biostudies-literatureSchuler EENIGMS NIH HHS3365-70https://www.ebi.ac.uk/biostudies/studies/S-EPMC5019822biostudies-literatureUnknown7(17)The mechanism of protein insertion into a lipid bilayer is poorly understood because the kinetics of this process is difficult to measure. We developed a new approach to study insertion of the antimicrobial peptide Mastoparan X into zwitterionic lipid vesicles, using a laser-induced temperature-jump to initiate insertion on the microsecond time scale and infrared and fluorescence spectroscopies to follow the kinetics. Infrared probes the desolvation of the peptide backbone and yields biphasic kinetics with relaxation lifetimes of 12 and 117 ?s, whereas fluorescence probes the intrinsic tryptophan residue located near the N-terminus and yields a single exponential phase with a lifetime of 440 ?s. Arrhenius analysis of the temperature-dependent rates yields an activation energy for insertion of 96 kJ/mol. These results demonstrate the complexity of the insertion process and provide mechanistic insight into the interplay between peptides and the lipid bilayer required for peptide transport across cellular membranes.The journal of physical chemistry lettersSubmillisecond Dynamics of Mastoparan X Insertion into Lipid Membranes.PMC5019822R01 GM053640Nagarajan SDyer RBSchuler EEfalseSubmillisecond Dynamics of Mastoparan X Insertion into Lipid Membranes.The mechanism of protein insertion into a lipid bilayer is poorly understood because the kinetics of this process is difficult to measure. We developed a new approach to study insertion of the antimicrobial peptide Mastoparan X into zwitterionic lipid vesicles, using a laser-induced temperature-jump to initiate insertion on the microsecond time scale and infrared and fluorescence spectroscopies to follow the kinetics. Infrared probes the desolvation of the peptide backbone and yields biphasic kinetics with relaxation lifetimes of 12 and 117 ?s, whereas fluorescence probes the intrinsic tryptophan residue located near the N-terminus and yields a single exponential phase with a lifetime of 440 ?s. Arrhenius analysis of the temperature-dependent rates yields an activation energy for insertion of 96 kJ/mol. These results demonstrate the complexity of the insertion process and provide mechanistic insight into the interplay between peptides and the lipid bilayer required for peptide transport across cellular membranes.2016-01-01T00:00:00Z2016 Sep2020-10-29T14:45:16Z2019-03-27T02:23:59ZS-EPMC50198222751301410.1021/acs.jpclett.6b01512