The results indicated that amounts of IF1 are lower by ∼23% in the 30S fraction from E. coli cells coexpressing U791 ribosomes and IF1 than Natural Product Library datasheet those expressing G791 ribosomes and IF1 (Fig.

2c). The composition of ribosomal proteins in both 30S fractions was similar (Fig. 2c), indicating that the U791 mutation does not affect assembly of ribosomal proteins to 16S rRNA. Considering that the proportion of mutant 30S subunits in the 30S peak from the sucrose gradient analysis is ∼40% (data not shown here), we conclude that the U791 mutation severely inhibits IF1 binding to the 30S ribosomal subunit. Overexpression of IF1 resulted in increased ribosomal subunit association, probably by stabilizing P-site-bound initiator tRNA, which is mediated by its cooperation with IF2 and its interaction with the initiation codon of the mRNA (Hartz et al., 1990; Wu & RajBhandary, 1997; Meinnel et al., 1999). Although no clear function has been assigned to initiation factor 1, considering that IF1 is known to aid IF2 and IF3 in translational initiation and increase the rate of both subunit association

and dissociation (Grunberg-Manago et al., 1975), and that IF1 footprinting mimics A-site-bound tRNA, a local PD-166866 datasheet change in the A-site due to an increase in IF1 binding to the A-site may be transmitted to the P-site (790 loop), thus restoring the functional conformation of the P-site for initiator tRNA binding and consequent ribosomal subunit association. The crystal structures of ribosomes also support this hypothesis. The 790 loop interacts with the 900 region and the 900 region docks somewhere in the vicinity of residues at positions 1413–1418 and 1483–1487 (Cate et al., 1999; Clemons et al., 1999), which interact with Tolmetin IF1 (Carter et al., 2001). We thank Dr John W.B. Hershey for providing us with a monoclonal antibody to IF1. This research was supported by the Pioneer Research Center Program (20100002201) through the National Research Program of Korea and NRF grant (2010-0008539) funded by the Ministry of Education, Science

and Technology. “
“The limited information on the genetic differences among the 15 currently known serotypes of Actinobacillus pleuropneumoniae has significantly hampered the development of typing-based diagnostic methods and multivalent vaccines. In this study, we compared the genomic differences between A. pleuropneumoniae strains CVCC259 (serotype 1) and CVCC261 (serotype 3) by representational difference analysis. Of the eight differential DNA sequences in the CVCC259 strain and 11 differential DNA sequences in the CVCC261 strain that we identified, seven represent known virulent genes, 10 encode putative proteins, and two encode hypothetical proteins. We also investigated the distribution of these 19 sequences among the 15 serotypes, and each serotype showed a different distribution pattern. The autotransporter adhesin occurred as a novel putative virulence factor in serotypes 1, 5, 7, 8, 9, and 11.