Charged amino acids in a preprotein inhibit SecA-dependent protein translocation.
Sec translocase catalyzes membrane protein insertion and translocation. We have introduced stretches of charged amino acid residues into the preprotein proOmpA and have analyzed their effect on in vitro protein translocation into Escherichia coli inner membrane vesicles. Both negatively and positively charged amino acid residues inhibit translocation of proOmpA, yielding a partially translocated polypeptide chain that blocks the translocation site and no longer activates preprotein-stimulated SecA ATPase activity. Stretches of positively charged residues are much stronger translocation inhibitors and suppressors of the preprotein-stimulated SecA ATPase activity than negatively charged residues. These results indicate that both clusters of positively and negatively charged amino acids are poor substrates for the Sec translocase and that this is reflected by their inability to stimulate the ATPase activity of SecA.
Nouwen
Nico
N
Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9751 NN Haren, The Netherlands.
Berrelkamp
Greetje
G
Driessen
Arnold J M
AJ
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D021381:Protein Transport; D018892:Proton-Motive Force; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013329:Structure-Activity Relationship
D000596:Amino Acids; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; D011498:Protein Precursors; D000069816:SEC Translocation Channels; C078167:OMPA outer membrane proteins; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins