Bacterial sec-translocase unfolds and translocates a class of folded protein domains.
It is generally assumed that preprotein substrates must be presented in an unfolded state to the bacterial Sec-translocase in order to be translocated. Here, we have examined the ability of the Sec-translocase to translocate folded preproteins. Tightly folded human cardiac Ig-like domain I27 fused to the C terminus of proOmpA is translocated efficiently by the Sec-translocase and the translocation kinetics are determined by the extent of folding of the titin I27 domain. Accumulation of specific translocation intermediates around the fusion point that undergo translocation progress upon ATP binding suggests that the motor protein SecA plays an important and decisive role in promoting unfolding of the titin I27 domain. It is concluded that the bacterial Sec-translocase is capable of actively unfolding preproteins.
Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and the Materials Science Center Plus, University of Groningen, 9751 NN, Haren, The Netherlands.
Nico
N
Nouwen
Greetje
G
Berrelkamp
Arnold J M
AJ
Driessen
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D064211:Connectin; D004926:Escherichia coli / Q000201:enzymology*; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009124:Muscle Proteins / Q000737:chemistry* / Q000378:metabolism*; D011489:Protein Denaturation / Q000187:drug effects; D017510:Protein Folding; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D014508:Urea / Q000494:pharmacology
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D064211:Connectin; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; D009124:Muscle Proteins; D000069816:SEC Translocation Channels; C577285:TTN protein, human; C078167:OMPA outer membrane proteins; D000255:Adenosine Triphosphate; D014508:Urea; D011494:Protein Kinases; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins