Features of transmembrane segments that promote the lateral release from the translocase into the lipid phase.
Topogenic sequences direct the membrane topology of proteins by being recognized and decoded by integral membrane translocases. In this paper, we have compared the minimal sequence characteristics of helical-hairpin, reverse signal-anchor, and stop-transfer sequences in bacterial membrane proteins that use either the YidC or SecYEG translocases for membrane insertion. We find that a stretch composed of 3 leucines and 16 alanines is required for efficient membrane-anchoring of the M13 procoat protein that inserts by a helical hairpin mechanism, and that a stretch composed of only 19 alanines has a detectable membrane-anchoring ability. Similar results were obtained for the reverse signal-anchor sequence of the single-spanning Pf3 coat protein and for stop-transfer segments engineered into leader peptidase. We have also determined the contribution to the apparent free energy of membrane insertion of M13 procoat for all 20 amino acids. The relative order of the contributions is similar to that determined for a stop-transfer sequence in the mammalian endoplasmic reticulum, but the absolute difference between the contributions for the most hydrophobic and most hydrophilic residues is somewhat larger in the E. coli system. These results are significant because they define the features of a membrane protein transmembrane segment that induce lateral release from the YidC and Sec translocases into the lipid bilayer in bacteria.
Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, Ohio 43210, USA.
Kun
K
Xie
Tara
T
Hessa
Susanna
S
Seppälä
Mikaela
M
Rapp
Gunnar
G
von Heijne
Ross E
RE
Dalbey
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D017104:Bacteriophage M13 / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D050356:Lipid Metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000378:metabolism; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; C412443:YIDC protein, E coli; D010447:Peptide Hydrolases; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins