Membrane insertion characteristics of the various transmembrane domains of the Escherichia coli TolQ protein.

Abstract

The Escherichia coli TolQ protein is a 230-amino acid integral cytoplasmic membrane protein required for the import of group A colicins, for infection by the filamentous phage, and for maintenance of the integrity of the bacterial envelope. TolQ is a polytopic protein with three membrane-spanning regions. The first membrane-spanning region has a 19-residue periplasmic NH2-terminal tail, while the second and third membrane-spanning segments are separated by a short 17-amino acid periplasmic loop. To study the membrane assembly of TolQ, fusions of different membrane-spanning regions were examined for their ability to insert in the absence of functional SecA or the membrane potential. Fusions containing the first membrane-spanning region plus the adjacent cytoplasmic domain and a construct containing the "hairpin loop," formed by the second and third membrane-spanning regions, insert in the absence of functional SecA. The fusion containing the second and third membrane-spanning regions required the membrane potential for insertion while the first membrane-spanning region was able to insert even in the absence of a membrane potential. Taken together, these results suggest that insertion of intact TolQ is not dependent on the Sec system, but does require the membrane potential.

• Authors: T M Lewin, R E Webster
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 271 Issue 24 Pg. 14143-9 (Jun 14 1996) ISSN: 0021-9258 [Print] United States
• PMID: 8662905 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Azides
• Bacterial Proteins
• Escherichia coli Proteins
• Membrane Proteins
• Membrane Transport Proteins
• Peptide Fragments
• Recombinant Fusion Proteins
• SEC Translocation Channels
• tolQ protein, E coli
• Carbonyl Cyanide m-Chlorophenyl Hydrazone
• Trypsin
• Adenosine Triphosphatases
• SecA Proteins

Topics

• Adenosine Triphosphatases (metabolism)
• Azides (pharmacology)
• Bacterial Proteins (chemistry, metabolism)
• Carbonyl Cyanide m-Chlorophenyl Hydrazone (pharmacology)
• Cell Membrane (metabolism, ultrastructure)
• Escherichia coli (metabolism)
• Escherichia coli Proteins
• Gene Expression (drug effects)
• Membrane Potentials
• Membrane Proteins (chemistry, metabolism)
• Membrane Transport Proteins
• Models, Structural
• Peptide Fragments (isolation & purification)
• Protein Structure, Secondary
• Recombinant Fusion Proteins (chemistry, metabolism)
• SEC Translocation Channels
• SecA Proteins
• Trypsin