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Molecular biology of G protein alpha subunits from bovine photoreceptors and the nematode Caenorhabditis elegans


Lochrie, Michael Alan (1991) Molecular biology of G protein alpha subunits from bovine photoreceptors and the nematode Caenorhabditis elegans. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/zqph-5443.


This thesis examines the molecular biology of G protein alpha subunits from bovine photoreceptors and the nematode Caenorhabditis elegans.

Chapter one describes the nucleotide sequence of the bovine cone photoreceptor transducin alpha subunit (Tc[alpha]). Analysis of the sequence defined regions homologous to other GTP binding proteins which may be involved in guanine nucleotide binding, allowed the positions of amino acids which are ADP-ribosylated by pertussis toxin and cholera toxin to be determined, and led to the prediction that G proteins are posttranslationally modified with lipids, which serve to anchor G protein alpha subunits to membranes. Comparison of the Tc[alpha] amino acid sequence with other alpha subunit sequences as they became available provided the first indications that G proteins would be more numerous and diverse than previously thought. The diversity observed among G protein subunits and its structural and functional implications are reviewed in the introduction.

In Chapter 2 the characterization of G protein alpha subunits in the nematode C. elegans is described. Two genes were isolated and their DNA sequences were determined. The protein products of these genes appear to be unique to C. elegans. A cDNA encoding a homolog of Go[alpha] was also isolated and sequenced. Thus, C. elegans has identifiable homologs of mammalian G proteins as well as G proteins that may be unique to it. The chromosomal positions of the genes were determined. Each maps to a unique location near mutations that could be in G protein alpha subunits.

In Appendix 1 the characterization of photoreceptor specific gene expression in human retinoblastoma cultures is described. These cells express cone photoreceptor-specific genes, but not rod photoreceptor specific genes. Therefore they may provide a system for studying the DNA elements required for the expression of genes specifically in cone cells.

Appendix 2 surveys systems for the heterologous expression of transducin alpha subunits in E. coli, yeast, and insect cells. The E. coli expression system offers the most promise for obtaining adequate amounts of active, pure protein.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Major Option:Biology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Simon, Melvin I.
Thesis Committee:
  • Simon, Melvin I. (chair)
  • Wold, Barbara J.
  • Lester, Henry A.
  • Tanouye, Mark
  • Kennedy, Mary B.
  • Sternberg, Paul W.
Defense Date:29 August 1990
Record Number:CaltechETD:etd-07092007-132214
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2842
Deposited By: Imported from ETD-db
Deposited On:23 Jul 2007
Last Modified:16 Apr 2021 22:14

Thesis Files

PDF (Lochrie_ma_1991.pdf) - Final Version
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