Biophysical and enzymatic properties of aminoglycoside adenylyltransferase AadA6 from Pseudomonas aeruginosa

AbstractThe gene coding for the aminoglycoside adenylyltransferase (aadA6) from a clinical isolate of Pseudomonas aeruginosa was cloned and expressed in Escherichia coli strain BL21(DE3)pLysS. The overexpressed enzyme (AadA6, 281 amino-acid residues) and a carboxy-terminal truncated variant molecule ([1-264]AadA6) were purified to near homogeneity and characterized. Light scattering experiments conducted under low ionic strength supported equilibrium between monomeric and homodimeric arrangements of the enzyme subunits. Circular Dichroism spectropolarimetry indicated a close structural relation to adenylate kinases. Both forms modified covalently the aminoglycosides streptomycin and spectinomycin. The enzyme required at least 5mM MgCl2 for normal Michaelis–Menten kinetics. Streptomycin exhibited a strong substrate inhibition effect at 1mM MgCl2. The truncated 17 residues at the C-terminus have little influence on protein folding, whereas they have a positive effect on the enzymic activity and stabilize dimers at high protein concentrations (>100μM). Homology modelling and docking based on known crystal structures yielded models of the central ternary complex of monomeric AadA6 with ATP and streptomycin or spectinomycin

Clinical and radiological efficacy of initial vs delayed treatment with infliximab plus methotrexate in patients with early rheumatoid arthritis

= 6 months, IFX was tapered and finally stopped. We aimed to correct for allocation bias using propensity scores. Functional ability was measured by the Health Assessment Questionnaire (HAQ), radiological progression by Sharp/van der Heijde scoring (SHS). Results: Baseline differences between the initial and delayed groups were no longer significant after propensity score adjustment. At 3 years after baseline, patients treated with initial MTX+IFX experienced more improvement in HAQ over time and were less likely to have SHS progression than patients treated with delayed MTX+IFX (p = 0.034). At 2 years after IFX initiation, more patients in the initial group compared with the delayed group could discontinue IFX after a good response (56% vs 29%, p = 0.008). Conclusions: The results of this post hoc analysis suggest that using MTX+IFX as initial treatment for patients with recent onset RA is more effective than reserving MTX+IFX for patients who failed on traditional DMARDs, with more HAQ improvement over time, more IFX discontinuation and less progression of joint damag

Age affects joint space narrowing in patients with early active rheumatoid arthritis

Background: Joint space narrowing ( JSN) in rheumatoid arthritis (RA) may be a manifestation of (primary) osteoarthritis becoming more prominent with age. We investigated the severity and predictors of JSN progression among different age groups. Methods: 10-year follow-up data of the BeSt study, a randomised controlled treat-to-target trial in early RA were used. Annual X-rays of hands and feet were scored using the Sharp/van der Heijde score (SHS). Subgroups were defined by age at baseline: 55, 40<55 and <40 years. JSN progression predictors were assessed by Poisson regression. Results: Baseline JSN scores (median (IQR)) were igher in patients 55 (2.0 (0.0-6.0)) compared with the other age groups: 1.0 (0.0-3.0) 40<55 and 0.3 (0.0-3.0) <40, p<0.001. After 10 years, total JSN and SHS were similar in all age groups. In patients 55 the mean erythrocyte sedimentation rate (ESR) over time (relative risk 1.02 (95% CI 1.00 to 1.03)

Feasibility of tailored treatment based on risk stratification in patients with early rheumatoid arthritis

Introduction: Personalized medicine is the holy grail of medicine. The EULAR recommendations for the management of rheumatoid arthritis (RA) support differential treatment between patients with baseline characteristics suggestive of a non-poor prognosis (non-PP) or poor prognosis (PP) (presence of autoantibodies, a high inflammatory activity and damage on radiographs). We aimed to determine which prognostic risk groups benefit more from initial monotherapy or initial combination therapy. Methods: 508 patients were randomized t

Drug-free remission, functioning and radiographic damage after 4 years of response-driven treatment in patients with recent-onset rheumatoid arthritis

0.05, group 4 versus groups 1 and 2, group 3 versus group 2). Conclusions: In patients with recent-onset active RA, drug-free remission was achieved in up to 18% of patients. DAS-driven treatment maintained clinical and functional improvement, independent of the treatment strategy. Joint damage progression remained significantly lower after initial combination therapy compared with initial monotherap

Major infections during methotrexate treatment for rheumatoid arthritis

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