Borrelia burgdorferi BBA74, a periplasmic protein associated with the outer membrane, lacks porin-like properties.
The outer membrane of Borrelia burgdorferi, the causative agent of Lyme disease, contains very few integral membrane proteins, in contrast to other gram-negative bacteria. BBA74, a Borrelia burgdorferi plasmid-encoded protein, was proposed to be an integral outer membrane protein with putative porin function and designated as a 28-kDa outer membrane-spanning porin (Oms28). In this study, the biophysical properties of BBA74 and its subcellular localization were investigated. BBA74 is posttranslationally modified by signal peptidase I cleavage to a mature 25-kDa protein. The secondary structure of BBA74 as determined by circular dichroism spectroscopy consists of at least 78% alpha-helix with little beta-sheet structure. BBA74 in intact B. burgdorferi cells was insensitive to proteinase K digestion, and indirect immunofluorescence microscopy showed that BBA74 was not exposed on the cell surface. Triton X-114 extraction of outer membrane vesicle preparations indicated that BBA74 is not an integral membrane protein. Taken together, the data indicate that BBA74 is a periplasmic, outer membrane-associated protein that lacks properties typically associated with porins.
Mulay
Vishwaroop
V
Department of Microbiology and Immunology, New York Medical College, Valhalla, NY 10595, USA.
Caimano
Melissa J
MJ
Liveris
Dionysios
D
Desrosiers
Daniel C
DC
Radolf
Justin D
JD
Schwartz
Ira
I
D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology; D019084:Fluorescent Antibody Technique, Indirect; D033903:Periplasmic Proteins / Q000032:analysis / Q000737:chemistry*; D018272:Porins / Q000737:chemistry* / Q000502:physiology; D017433:Protein Structure, Secondary
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D033903:Periplasmic Proteins; D018272:Porins; C100895:protein Oms28, Borrelia burgdorferi