Interesting sequence differences between the pilin gene inversion regions of Moraxella lacunata ATCC 17956 and Moraxella bovis Epp63

Abstract

The bacterium Moraxella lacunata is a causative agent of human conjunctivitis and keratitis. We have previously reported construction of plasmid pMxLl, which includes a 5.9-kb fragment on which the pilin gene inversion region of M. lacunata resides. The inversion region of pMxLl was shown to invert when pMxLl was in an Escherichia coli host cell. In this report, we present Western immunoblot analysis using Moraxelia bovis Epp63 anti-I and anti-Q pilin sera which demonstrate that pMxLl makes pilin only when in orientation 1. The type 4 (MePhe) class of bacterial pili is found on a wide variety of gram-negative bacteria (4), including Moraxella bovis (14) and Moraxella lacunata (12). The type 4 piliated (P+) bacteria of the family Neisseriaceae (including Moraxella, Branhamella, Neisseria, and other genera) display several phenotypic differences from the equivalent nonpiliated (P-) bacteria. These phenotypes include colony morphology, pitting of agar, autoagglutination, pellicle formation, hemagglutination, twitching motility, and increased competence for natural DNA transformation (for a review, see reference 10).We have been studying the type 4 pilin gene regions of M. bovis and M. lacunata. These organisms are very closely related, as determined by both DNA-DNA hybridization analysis (20) and transformation studies (2). M. bovis is the primary cause of bovine infectious keratoconjunctivitis (8), and M. lacunata is a pathogen which occasionally causes conjunctivitis in humans (3,16,19). A single strain of M. bovis is capable of producing one or the other of two pilin types, named Q (previously P) and I (previously x) for strain Epp63 (14,17). The switch in expression between the tfpQ and tfpl pilin genes is due to an inversion of a 2.1-kb region of DNA (5, 13). When tfpQ is in the expression locus it is in orientation 1, while orientation 2 has tfpI in the expression locus. We have shown that a gene (piv) adjacent to the inversion region is required for inversions to occur (12). We have described both similarities and differences between the * Corresponding author.

Multiple DNA Binding Activities of the Novel Site-specific Recombinase, Piv, from Moraxella lacunata

“…Previous examination of the DNA sequence of the inversion region of M. lacunata revealed 26-bp inverted repeats, invL and invR, which defined the left and right ends of the invertible element (17,18). Piv-mediated DNA cleavage and strand exchange must occur within these two 26-bp sequences for sitespecific DNA inversion of the pilin segment.…”

Transcriptional regulation of type 4 pilin genes and the site-specific recombinase gene, piv, in Moraxella lacunata and Moraxella bovis

“…The piv gene, located immediately adjacent to the invertible segment, encodes the putative site-specific DNA invertase (19,20). The pilin genes of M. lacunata share considerable homology with the pilin genes of M. bovis and are identically arranged (26). However, the M. lacunata tfpI gene contains a 19-bp perfect tandem repeat near the inversion junction site that creates a frameshift, resulting in a shortened, nonfunctional pilin gene product.…”

Piv Site-Specific Invertase Requires a DEDD Motif Analogous to the Catalytic Center of the RuvC Holliday Junction Resolvases

“…The DEDD residues are not essential for inv recombination site recognition and binding, but this acidic tetrad does appear to contribute to the stability of Piv-inv interactions. On the basis of these results, a working model for Piv-mediated inversion that includes resolution of a Holliday junction is presented.Piv catalyzes site-specific inversion of a 2.1-kb chromosomal segment encoding type 4 pilin genes of the human and cow eye pathogens Moraxella lacunata and Moraxella bovis, respectively (14,18,27). This DNA rearrangement results in phase variation of the type 4 pili (19) (Fig.…”

“…Piv catalyzes site-specific inversion of a 2.1-kb chromosomal segment encoding type 4 pilin genes of the human and cow eye pathogens Moraxella lacunata and Moraxella bovis, respectively (14,18,27). This DNA rearrangement results in phase variation of the type 4 pili (19) (Fig.…”