Structural Diversity in the Type IV Pili of Multidrug-resistant Acinetobacter.

Acinetobacter baumannii is a Gram-negative coccobacillus found primarily in hospital settings that has recently emerged as a source of hospital-acquired infections. A. baumannii expresses a variety of virulence factors, including type IV pili, bacterial extracellular appendages often essential for attachment to host cells. Here, we report the high resolution structures of the major pilin subunit, PilA, from three Acinetobacter strains, demonstrating that A. baumannii subsets produce morphologically distinct type IV pilin glycoproteins. We examine the consequences of this heterogeneity for protein folding and assembly as well as host-cell adhesion by Acinetobacter Comparisons of genomic and structural data with pilin proteins from other species of soil gammaproteobacteria suggest that these structural differences stem from evolutionary pressure that has resulted in three distinct classes of type IVa pilins, each found in multiple species.

Cataract-causing mutation R233H affects the stabilities of ßB1- and ßA3/ßB1-crystallins with different pH-dependence.

Disease-causing mutations can be stabilizing or destabilizing. Missense mutations of structural residues are generally destabilizing, while stabilizing mutations are usually linked to alterations in protein functions. Stabilizing mutations are rarely identified in mutations linked to congenital cataract, a disease caused by the opacification of the lens. In this research, we found that R233H mutation had little impact on ßB1-crystallin structure, solubility and thermal stability under neutral solution pH conditions. The mutation increased ßB1 stability against guanidine hydrochloride-induced denaturation, suggesting that Arg233 might be a functional residue. Further analysis indicated that the R233H mutation did not affect the formation of ßA3/ßB1 heteromer, but significantly reduced heteromer stability against heat- and guanidine hydrochloride-induced denaturation. The R233H mutation negatively affected the thermal stabilities and aggregatory propensities of ßB1 and ßA3/ßB1 with different pH-dependence, implying that the protonation of His side chains during acidification played a regulatory role in crystallin stability and aggregation. Molecular dynamic simulations indicated that Arg233 is one of the residues forming an inter-subunit ion-pairing network with intrinsically dynamic nature. Based on these observations, we proposed that the highly dynamic ion-pairing network contributed to the tradeoff among ßB1 solubility, stability, aggregatory propensity and function of protecting ßA3.

[Different entry points of needle knife for lumbar disc herniation: a randomized controlled trial].

OBJECTIVE: To compare the clinical efficacy and safety among three different entry points of needle knife, including tenderness point, intervertebral foramen point and articular process node, for lumbar disc herniation (LDH). METHODS: A total of 105 patients with LDH were randomly divided into a tenderness point group (35 cases, 1 case dropped off ), an intervertebral foramen point group (35 cases) and an articular process node group (35 cases, 1 case dropped off ). In the three groups, the needle knife was given at positive tenderness points of lumbosacral and hip, the external point of intervertebral foramen and the node of vertebral joint process respectively, once a week for a total of 4 times. The scores of Japanese Orthopaedic Association (JOA), Oswestry disability index (ODI), visual analogue scale (VAS) were recorded before treatment, 2 weeks and 4 weeks into treatment, and 3 months follow-up after treatment, and the clinical efficacy and safety was observed. RESULTS: Compared before treatment, the JOA scores in each group were increased 2, 4 weeks into treatment and in the follow-up (P<0.05); 4 weeks into treatment and in the follow-up, the JOA scores in the tenderness point group and the articular process node group were higher than those in the intervertebral foramen point group (P<0.05). Compared before treatment, except for ODI score 2 weeks into treatment in the intervertebral foramen point group, the ODI and VAS scores in each group were decreased 2, 4 weeks into treatment and in the follow-up (P<0.05), and the ODI scores in the tenderness point group and the articular process node group were lower than those in the intervertebral foramen point group (P<0.05). In 2 weeks into treatment, the VAS scores in the tenderness point group and the articular process node group were lower than those in the intervertebral foramen point group (P<0.05); in 4 weeks into treatment and follow-up, the VAS scores in the tenderness point group were lower than the other two groups (P<0.05). After treatment, the clinical efficacy of each group was similar (P>0.05); during the follow-up, the total effective rate in the tenderness point group was higher than that in the intervertebral foramen point group (P<0.05). There were no serious adverse events in each group. CONCLUSION: The three different entry points of needle knife all could improve the symptoms of patients with LDH. The comprehensive effect of improving the subjective symptoms, lumbar function, pain degree and long-term curative effect is better in the tenderness point group.