Activation of the Arp2/3 complex by the Listeria acta protein. Acta binds two actin monomers and three subunits of the Arp2/3 complex.

ActA is a bacterially encoded protein that enables Listeria monocytogenes to hijack the host cell actin cytoskeleton. It promotes Arp2/3-dependent actin nucleation, but its interactions with cellular components of the nucleation machinery are not well understood. Here we show that two domains of ActA (residues 85-104 and 121-138) with sequence similarity to WASP homology 2 domains bind two actin monomers with submicromolar affinity. ActA binds Arp2/3 with a K(d) of 0.6 microm and competes for binding with the WASP family proteins N-WASP and Scar1. By chemical cross-linking, ActA, N-WASP, and Scar1 contact the same three subunits of the Arp2/3 complex, p40, Arp2, and Arp3. Interestingly, profilin competes with ActA for binding of Arp2/3, but actophorin (cofilin) does not. The minimal Arp2/3-binding site of ActA (residues 144-170) is C-terminal to both actin-binding sites and shares sequence homology with Arp2/3-binding regions of WASP family proteins. The maximal activity at saturating concentrations of ActA is identical to the most active domains of the WASP family proteins. We propose that ActA and endogenous WASP family proteins promote Arp2/3-dependent nucleation by similar mechanisms and require simultaneous binding of Arp2 and Arp3.

[Reflux gastritis due to Helicobacter pylori as the cause of unsatisfactory results of cholecystectomy]. / Refliuks-gastrit, obuslovlennyi Helicobacter pylori, kak prichina neudovletvoritel'nogo rezul'tata kholetsistéktomii.

In 85.8% of patients with cholelithiasis (CL) the reflux-gastritis was revealed, of whom in 71.4% caused by Helicobacter pylori. In 80% of patients the positive effect achievement is guaranteed by the early accomplishment of cholecystectomy and an active conduction of rehabilitation measures in early postoperative period.

[Status of humoral immunity in patients with severe craniocerebral injuries in the acute and late periods]. / Sostoianie gumoral'nogo immuniteta u bol'nykh s tiazheloi cherepno-mozgovoi travmoi v ostrom i otdalennom periodakh.

A group of 105 patients with contusion foci in the brain was studied for humoral immunity (determinations of IgA, IgG and IgM) in the process of their surgical and conservative treatment, on days 1, 7, 21, 30 and 60. and at 1, 3 and 5 years following contusion foci removal. The decreased levels of IgA, IgG and IgM were revealed at all periods of the traumatic disease. The greatest impairment of immunologic response was observed on day 1 and 7 of disease which was correlated with the severe status of patients, duration and depth of unconsciousness, the severity of general cerebral and focal symptomatology and with attendant bronchopulmonary complications. Immunological methods of investigation in conjunction with clinical ones are of great diagnostic and prognostic value.