Structural basis for the interaction of lipopolysaccharide with outer membrane protein H (OprH) from Pseudomonas aeruginosa

Solution NMR spectroscopy for the determination of structures of membrane proteins in a lipid environment

Several recent advancements have transformed solution NMR spectroscopy into a competitive, elegant, and eminently viable technique for determining the solution structures of membrane proteins at the level of atomic resolution. Once a good level of cell-based or cell-free expression and purification of a suitably sized membrane protein has been achieved, then NMR offers a combination of several versatile strategies, for example, choice of appropriate deuterated or non-deuterated detergents, temperature, and ionic strength; isotope labelling with (2)H, (13)C, (15)N, with or without protonation of Ile (δ1), Leu, and Val methyl protons; combinatorial labelling of specific amino acids; transverse relaxation-optimized NMR spectroscopy-based, Nonuniform sampling-based, and other NMR experiments; measurement of residual dipolar couplings using stretched polyacrylamide gels or DNA nanotubes; and spin-labelling and paramagnetic relaxation enhancements. Strategic combinations of these advancements together with availability of highly sensitive cryogenically cooled probes equipped high-field NMR spectrometers (up to 1 GHz (1)H frequency) have allowed the perseverant investigator to successfully overcome several of the conventional pitfalls associated with the NMR technique and membrane proteins, viz., low sensitivity, poor sample stability, spectral crowding, and a limited number of NOEs and other constraints for structure calculations. This has resulted in an unprecedented growth in the number of successfully determined NMR structures of large and complex membrane proteins, and this technique now holds great promise for the structure determination of an ever larger body of membrane proteins.

Mucosal and systemic antibody responses to potential Pseudomonas aeruginosa vaccine protein antigens in young children with cystic fibrosis following colonization and infection

Pseudomonas aeruginosa is an important prognostic determinant in cystic fibrosis (CF). Little is known however, about P. aeruginosa induced local mucosal and systemic immune responses. Twenty CF children were categorized according to their P. aeruginosa status: (1) chronic lower respiratory tract infection (LRTI), (2) prior successfully treated initial LRTI, (3) isolated upper respiratory tract (URT) colonization, and (4) no known URT colonization or previous LRTI. Their antibody responses, and those of six non-CF disease controls, in serum and bronchoalveolar lavage (BAL) fluid to potential P. aeruginosa vaccine antigens outer membrane protein F (OprF), outer membrane protein H (OprH), catalase A (KatA) and a whole killed cell (WKC) extract were evaluated. Outer membrane protein G (OprG) responses were also measured in blood. Natural exposure, colonization and infection resulted in detectable antibody levels in BAL and serum in all CF groups. Both chronically infected and URT colonized CF children had substantially elevated immunoglobulin A antibody levels in the BAL fluid and sera toward the WKC extract and OprF antigen compared with the other groups of CF children and non-CF controls. The serum levels of specific P. aeruginosa antibodies involving immunoglobulin G and M isotypes increased with chronic LRTI, especially antibody levels to KatA, OprH and WKC extract, which were substantially greater in chronically infected children compared with all other groups. In conclusion, natural exposure, URT colonization and LRTI with P. aeruginosa all induce substantial mucosal and systemic antibody responses to potential vaccine antigens with chronically infected CF children having the highest levels.

Emergence of antibiotic-resistant extremophiles (AREs)

Excessive use of antibiotics in recent years has produced bacteria that are resistant to a wide array of antibiotics. Several genetic and non-genetic elements allow microorganisms to adapt and thrive under harsh environmental conditions such as lethal doses of antibiotics. We attempt to classify these microorganisms as antibiotic-resistant extremophiles (AREs). AREs develop strategies to gain greater resistance to antibiotics via accumulation of multiple genes or plasmids that harbor genes for multiple drug resistance (MDR). In addition to their altered expression of multiple genes, AREs also survive by producing enzymes such as penicillinase that inactivate antibiotics. It is of interest to identify the underlying molecular mechanisms by which the AREs are able to survive in the presence of wide arrays of high-dosage antibiotics. Technologically, "omics"-based approaches such as genomics have revealed a wide array of genes differentially expressed in AREs. Proteomics studies with 2DE, MALDI-TOF, and MS/MS have identified specific proteins, enzymes, and pumps that function in the adaptation mechanisms of AREs. This article discusses the molecular mechanisms by which microorganisms develop into AREs and how "omics" approaches can identify the genetic elements of these adaptation mechanisms. These objectives will assist the development of strategies and potential therapeutics to treat outbreaks of pathogenic microorganisms in the future.