The F286Y mutation of PrlA4 tempers the signal sequence suppressor phenotype by reducing the SecA binding affinity.
SecYEG forms the protein-conducting channel of the Escherichia coli translocase. It binds the peripheral ATPase SecA that drives the preprotein translocation reaction. PrlA4 is a double mutant of SecY that enables the translocation of preproteins with a defective or even missing signal sequence. The effect of the individual mutations, F286Y and I408N, was studied with SecYEG proteoliposomes. SecY(I408N) is responsible for the increased translocation of preproteins with a defective and normal signal sequence, and exhibits a stronger prl phenotype than PrlA4. This activity correlates with an elevated SecA-translocation ATPase and SecA binding affinity. SecY(F286Y) supports only a low SecA binding affinity, preprotein translocation and SecA translocation ATPase activity. These results suggest that the second site F286Y mutation reduces the strength of the I408N mutation of PrlA4 by lowering the SecA binding affinity.
de Keyzer
Jeanine
J
Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
van der Does
Chris
C
Swaving
Jelto
J
Driessen
Arnold J M
AJ
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D029968:Escherichia coli Proteins; D006361:Heating; D026901:Membrane Transport Proteins / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D021382:Protein Sorting Signals; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D000069816:SEC Translocation Channels; C057841:SecY protein, E coli; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins