The brownian ratchet and power stroke models for posttranslational protein translocation into the endoplasmic reticulum.
A quantitative analysis of experimental data for posttranslational translocation into the endoplasmic reticulum is performed. This analysis reveals that translocation involves a single rate-limiting step, which is postulated to be the release of the signal sequence from the translocation channel. Next, the Brownian ratchet and power stroke models of translocation are compared against the data. The data sets are simultaneously fit using a least-squares criterion, and both models are found to accurately reproduce the experimental results. A likelihood-ratio test reveals that the optimal fit of the Brownian ratchet model, which contains one fewer free parameter, does not differ significantly from that of the power stroke model. Therefore, the data considered here cannot be used to reject this import mechanism. The models are further analyzed using the estimated parameters to make experimentally testable predictions.
Elston
Timothy C
TC
Biomathematics Graduate Program/Department of Statistics, North Carolina State University, Raleigh, North Carolina 27695-8203, USA. elston@stat.ncsu.edu
D000465:Algorithms; D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D016018:Least-Squares Analysis; D016013:Likelihood Functions; D015233:Models, Statistical; D008962:Models, Theoretical; D009010:Monte Carlo Method; D011485:Protein Binding; D021381:Protein Transport; D013997:Time Factors