Cloning and characterization of the structural gene for the class 2 protein of Neisseria meningitidis

Abstract

The class 2 protein of Neisseria meningitidis is the major outer membrane protein and a porin. A λgt11 bank of meningococcal chromosomal DNA was screened with monoclonal antibodies against gonococcal protein IB that cross-react with meningococcal class 2 protein. Three independent immunoreactive clones were isolated. DNA sequence analysis indicated that these clones included regions encoding the N-terminal portion of the class 2 protein. An oligonucleotide of 21 bases that was complementary to this sequence was synthesized and used as a probe for a second screening of the λ gt11 bank. One of the positive clones isolated contained the complete gene, including the ribosome binding site, but lacked the promoter region. On the basis of the DNA sequence, a protein of 360 amino acids was predicted. Comparison of the predicted protein sequence with that of gonococcal protein I showed little homology in six regions constituting 29% of the total amino acids, while the remainder of the coding frame showed 81% homology of amino acid residues. The DNA homology in the immediate 5' and 3' noncoding sequences was very striking. Following the putative transcription terminator, the 3' DNA sequence contained a complex pattern of direct and inverted repeats having some similarity to the 3' sequence of the gonococcal protein IB gene and very close homology to a sequence located in the pilS1 region (R. Haas and T.F. Meyer, Cell 44:107, 1986), an area of the gonococcal genome containing silent pilin genes.