Parallel effects of signal peptide hydrophobic core modifications on cotranslational translocation and posttranslational cleavage by purified signal peptidase
Cioffi, Joseph Armand
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/23340
Description
Title
Parallel effects of signal peptide hydrophobic core modifications on cotranslational translocation and posttranslational cleavage by purified signal peptidase
Author(s)
Cioffi, Joseph Armand
Issue Date
1989
Department of Study
Molecular and Integrative Physiology
Discipline
Molecular and Integrative Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Language
eng
Abstract
Secretory proteins are targeted to the secretory pathway by an amino terminal extension sequence known as the signal peptide. Signal peptides contain a central core of uncharged amino acids that are usually hydrophobic in nature. The hydrophobic core of the parathyroid hormone (PTH) signal peptide is composed of 12 contiguous hydrophobic amino acids. Although the exact role of the core in signal peptide function is not well defined, particularly in mammalian systems, its length and hydrophobicity have been shown to be important characteristics. To determine the requirements for length and hydrophobicity of a mammalian hydrophobic core, amino acids were substituted and deleted from this region of the PTH signal peptide and the effects on protein translocation and processing were examined in a mammalian cell-free system. Increasing the length of the core by 3 residues had little effect on translocation and processing of the mutant signal peptide by microsomal membranes. Decreasing the length of the core by 6 residues abolished signal activity and partially blocked its interaction with signal recognition particle. Deleting only 2 residues from the core resulted in a position dependent effect on translocation and processing by microsomal membranes that was unrelated to core hydrophobicity but correlated inversely with core amphiphilicity. Deletion at the N-terminus of the core caused a significant decrease in signal activity while deletions at the C-terminus had little effect. Signal activity improved as the position of the pair-wise deletion moved from the N-terminus to the C-terminus of the core. Precursor proteins containing defective signal peptides were unable to translocate across the microsomal membrane. Parallel effects of these modifications on post-translational cleavage by purified signal peptidase were observed. A model is proposed to explain these parallel effects.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
