Purification, cloning, and sequence of outer membrane protein P1 of Haemophilus influenzae type b

Outer membrane protein P1 from Haemophilus influenzae type b MinnA was purified and partially characterized. Antiserum was generated against the purified protein and was used to immunologically screen a lamba EMBL3 genomic library prepared from strain MinnA DNA. A 4.2-kilobase-pair EcoRI-BamHI fragment containing the P1 gene was subcloned into pBR322. The recombinant protein was synthesized by Escherichia coli K-12, in which it localized to the outer membrane. The N-terminal sequence of the purified protein was determined and found to correspond to residues 23 through 36. The 22-amino-acid leader peptide had a typical structure, with two lysine residues near the amino terminus, a stretch of hydrophobic residues, and alanine residues at positions 20 and 22. The Mr of the processed protein was 47,752, which is in good agreement with the estimate of 50,000 from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Putative -35 and -10 promoter sequences were identified upstream from the translational start site. Codon usage was examined and determined to be substantially different than the codon preference in E. coli.