TP0453, a concealed outer membrane protein of Treponema pallidum, enhances membrane permeability.
The outer membrane of Treponema pallidum, the non-cultivable agent of venereal syphilis, contains a paucity of protein(s) which has yet to be definitively identified. In contrast, the outer membranes of gram-negative bacteria contain abundant immunogenic membrane-spanning beta-barrel proteins mainly involved in nutrient transport. The absence of orthologs of gram-negative porins and outer membrane nutrient-specific transporters in the T. pallidum genome predicts that nutrient transport across the outer membrane must differ fundamentally in T. pallidum and gram-negative bacteria. Here we describe a T. pallidum outer membrane protein (TP0453) that, in contrast to all integral outer membrane proteins of known structure, lacks extensive beta-sheet structure and does not traverse the outer membrane to become surface exposed. TP0453 is a lipoprotein with an amphiphilic polypeptide containing multiple membrane-inserting, amphipathic alpha-helices. Insertion of the recombinant, non-lipidated protein into artificial membranes results in bilayer destabilization and enhanced permeability. Our findings lead us to hypothesize that TP0453 is a novel type of bacterial outer membrane protein which may render the T. pallidum outer membrane permeable to nutrients while remaining inaccessible to antibody.
Hazlett
Karsten R O
KR
Center for Microbial Pathogenesis, University of Connecticut Health Center, 263 Farmington Ave., Farmington, Connecticut 06030, USA. KHazlett@up.uchc.edu
Cox
David L
DL
Decaffmeyer
Marc
M
Bennett
Michael P
MP
Desrosiers
Daniel C
DC
La Vake
Carson J
CJ
La Vake
Morgan E
ME
Bourell
Kenneth W
KW
Robinson
Esther J
EJ
Brasseur
Robert
R
Radolf
Justin D
JD
D000954:Antigens, Surface / Q000502:physiology*; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000502:physiology*; D014210:Treponema pallidum / Q000737:chemistry*
D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins