Charge composition features of model single-span membrane proteins that determine selection of YidC and SecYEG translocase pathways in Escherichia coli.
We have investigated the features of single-span model membrane proteins based upon leader peptidase that determines whether the proteins insert by a YidC/Sec-independent, YidC-only, or YidC/Sec mechanism. We find that a protein with a highly hydrophobic transmembrane segment that inserts into the membrane by a YidC/Sec-independent mechanism becomes YidC-dependent if negatively charged residues are inserted into the translocated periplasmic domain or if the hydrophobicity of the transmembrane segment is reduced by substituting polar residues for nonpolar ones. This suggests that charged residues in the translocated domain and the hydrophobicity within the transmembrane segment are important determinants of the insertion pathway. Strikingly, the addition of a positively charged residue to either the translocated region or the transmembrane region can switch the insertion requirements such that insertion requires both YidC and SecYEG. To test conclusions from the model protein studies, we confirmed that a positively charged residue is a SecYEG determinant for the endogenous proteins ATP synthase subunits a and b and the TatC subunit of the Tat translocase. These findings provide deeper insights into how pathways are selected for the insertion of proteins into the Escherichia coli inner membrane.
Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio 43210.
Lu
L
Zhu
Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio 43210.
Abdul
A
Wasey
Department of Physiology and Biophysics, University of California, Irvine, California 92697-4560.
Stephen H
SH
White
Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio 43210. Electronic address: dalbey@chemistry.ohio-state.edu.
Ross E
RE
Dalbey
D000595:Amino Acid Sequence; D001703:Biophysics / Q000379:methods; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000502:physiology*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010957:Plasmids / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D018892:Proton-Motive Force; D000069816:SEC Translocation Channels; D013816:Thermodynamics
D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C412443:YIDC protein, E coli