A porin from Klebsiella pneumoniae: sequence homology, three-dimensional model, and complement binding.
A recombinant plasmid containing ompK36, the gene coding for the Klebsiella pneumoniae outer membrane protein OmpK36, was constructed by transposon mutagenesis and subcloning. Clones were identified in a cosmid library in Escherichia coli on the basis of their reaction with antiserum against the OmpK36 protein and by the presence in gel electrophoretic analysis of a band in E. coli outer membranes migrating with a mobility corresponding to 36 kDa. The ompK36-encoded protein exhibited characteristic properties of porins, such as heat modifiability and resistance to trypsin. The sequence of the gene revealed that OmpK36 is a close relative of the enterobacterial porin family, with a high degree of homology with E. coli OmpC, PhoE, and OmpF. On the basis of the structures of OmpF and PhoE porins, determined previously by X-ray analysis, it appears likely that the three-dimensional structure of OmpK36 also contains the motif of a 16-stranded beta-barrel, with long loops on one end and short turns on the other. Like the OmpC porin from E. coli, OmpK36 contains a long insertion in loop 4. The results of a binding study of complement component C1q to OmpK36 and the analysis of the OmpK36 model suggest that C1q binding sites are covered by the lipopolysaccharide core in the native porin.
Albertí
S
S
Departamento de Biología Ambiental, Universidad de las Islas Baleares, Palma de Mallorca, Spain.
Rodríquez-Quiñones
F
F
Schirmer
T
T
Rummel
G
G
Tomás
J M
JM
Rosenbusch
J P
JP
Benedí
V J
VJ
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D003001:Cloning, Molecular; D015922:Complement C1q / Q000378:metabolism*; D005798:Genes, Bacterial / Q000235:genetics*; D007711:Klebsiella pneumoniae / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018272:Porins / Q000235:genetics* / Q000276:immunology; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; C092233:OmpK36 protein, Klebsiella pneumoniae; D018272:Porins; D015922:Complement C1q