Biophys J, March 2002, p. 1239-1253, Vol. 82, No. 3

The Brownian Ratchet and Power Stroke Models for Posttranslational Protein Translocation into the Endoplasmic Reticulum

Biomathematics Graduate Program/Department of Statistics, North Carolina State University, Raleigh, North Carolina 27695-8203 USA

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.

Biophys J, March 2002, p. 1239-1253, Vol. 82, No. 3
© 2002 by the Biophysical Society   0006-3495/02/03/1239/15  $2.00

This article has been cited by other articles:

				S. Hildebrandt, D. Raden, L. Petzold, A. S. Robinson, and F. J. Doyle III A Top-Down Approach to Mechanistic Biological Modeling: Application to the Single-Chain Antibody Folding Pathway Biophys. J., October 15, 2008; 95(8): 3535 - 3558. [Abstract] [Full Text] [PDF]

				R. Zandi, D. Reguera, J. Rudnick, and W. M. Gelbart What drives the translocation of stiff chains? PNAS, July 22, 2003; 100(15): 8649 - 8653. [Abstract] [Full Text] [PDF]