Cloning of fibA, encoding an immunogenic subunit of the fibril-like surface structure of Peptostreptococcus micros.
Although we are currently unaware of its biological function, the fibril-like surface structure is a prominent characteristic of the rough (Rg) genotype of the gram-positive periodontal pathogen Peptostreptococcus micros. The smooth (Sm) type of this species as well as the smooth variant of the Rg type (RgSm) lack these structures on their surface. A fibril-specific serum, as determined by immunogold electron microscopy, was obtained through adsorption of a rabbit anti-Rg type serum with excess bacteria of the RgSm type. This serum recognized a 42-kDa protein, which was subjected to N-terminal sequencing. Both clones of a lambdaTriplEx expression library that were selected by immunoscreening with the fibril-specific serum contained an open reading frame, designated fibA, encoding a 393-amino-acid protein (FibA). The 15-residue N-terminal amino acid sequence of the 42-kDa antigen was present at positions 39 to 53 in FibA; from this we conclude that the mature FibA protein contains 355 amino acids, resulting in a predicted molecular mass of 41,368 Da. The putative 38-residue signal sequence of FibA strongly resembles other gram-positive secretion signal sequences. The C termini of FibA and two open reading frames directly upstream and downstream of fibA exhibited significant sequence homology to the C termini of a group of secreted and surface-located proteins of other gram-positive cocci that are all presumably involved in anchoring of the protein to carbohydrate structures. We conclude that FibA is a secreted and surface-located protein and as such is part of the fibril-like structures.
Kremer
B H
BH
Department of Oral Microbiology, Academic Centre for Dentistry Amsterdam, Amsterdam, The Netherlands.
Bijlsma
J J
JJ
Kusters
J G
JG
de Graaff
J
J
van Steenbergen
T J
TJ
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000235:genetics* / Q000276:immunology; D003001:Cloning, Molecular; D015870:Gene Expression; D005838:Genotype; D008565:Membrane Proteins / Q000235:genetics* / Q000276:immunology; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010462:Peptostreptococcus / Q000235:genetics* / Q000276:immunology / Q000648:ultrastructure; D020449:Repetitive Sequences, Amino Acid; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D000942:Antigens, Bacterial; D008565:Membrane Proteins; C118696:fibA protein, bacteria