GSBS Student Publications

Student Author(s)

Steven F. Trueman

GSBS Program

Biochemistry & Molecular Pharmacology

UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology



Document Type


Medical Subject Headings

Amino Acid Motifs; Cathepsin A; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Kinetics; Membrane Transport Proteins; Multiprotein Complexes; Mutagenesis, Site-Directed; Mutation, Missense; Phenotype; Protein Binding; Protein Sorting Signals; Protein Structure, Tertiary; Protein Transport; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins


Biochemistry, Biophysics, and Structural Biology | Life Sciences | Medicine and Health Sciences


The transition between the closed and open conformations of the Sec61 complex permits nascent protein insertion into the translocation channel. A critical event in this structural transition is the opening of the lateral translocon gate that is formed by four transmembrane (TM) spans (TM2, TM3, TM7, and TM8 in Sec61p) to expose the signal sequence-binding site. To gain mechanistic insight into lateral gate opening, mutations were introduced into a lumenal loop (L7) that connects TM7 and TM8. The sec61 L7 mutants were found to have defects in both the posttranslational and cotranslational translocation pathways due to a kinetic delay in channel gating. The translocation defect caused by L7 mutations could be suppressed by the prl class of sec61 alleles, which reduce the fidelity of signal sequence recognition. The prl mutants are proposed to act by destabilizing the closed conformation of the translocation channel. Our results indicate that the equilibrium between the open and closed conformations of the protein translocation channel maintains a balance between translocation activity and signal sequence recognition fidelity.

Rights and Permissions

Citation: Mol Biol Cell. 2011 Sep;22(17):2983-93. Epub 2011 Jul 7. Link to article on publisher's website


© 2011 Trueman et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (

Related Resources

Link to article in PubMed

PubMed ID




To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.