Conformational aspects of beta-trypsin interactions with substrates and pancreatic trypsin inhibitor. II. Structure of tetrahedral adducts and acylenzyme

Theoretical conformational analysis of the tetrahedral complexes of trypsin with the N-acetyl-L-lysine methyl amide, which are formed at the acylation and the deacylation stages of the catalytical act has been carried out. The lowest energy conformations are shown to be productive ones. All favorable structures of N-acetyl-L-lysyl-trypsin and N-acetyl-L-arginyl-trypsin acylenzymes have been analysed. The global conformations of both complexes are found to be very similar with the structures providing for a transition to the second tetrahedral state. Conformations of the nonbonded, tetrahedral and acyl complexes with N-acetyl-L-lysine methyl amide are compared and the differences in orientation of atomic groups participating in the catalysis are revealed. All changes of optimal structures of the complexes indispensable for the catalytical process are shown to proceed in a spontaneous way without introduction of any intramolecular strain.     

The spatial organization and conformational flexibility of neuropeptides of the gallatostatin family

The spatial organization and conformational flexibility of neuropeptides of the gallatostatin family was studied by the method of theoretical conformational analysis. It was found that the spatial organization of neuropeptides allows the realization of folded helical structures of the C-terminal pentapeptide, and the flexibility of neuropeptides is due to a great number of low-energy states in the N-terminal fragment of the molecule.     

Free and Membrane-Bound Multienzyme Complexes with Calvin Cycle Activities in Cotton Leaves

Free and membrane-bound forms of Calvin-cycle multienzyme complexes with a mol wt of 520 ± 20 kD and 640 ± 25 kD, respectively, were isolated from the cotton (Gossypium hirsutum L.) leaves. Both complexes exhibited the following enzymatic activities: ribose phosphate isomerase, phosphoribulokinase, ribulose bisphosphate carboxylase (Rubisco), phosphoglycerate kinase, and glyceraldehyde phosphate dehydrogenase. The activities of the membrane-bound multienzyme complex were significantly higher than the activities of the free complex. This difference was especially pronounced in the case of carboxylase activity. An increase in the enzymatic activity of membrane-bound multienzyme complex in comparison with the free complex is presumably due to the different number of their constituent parts. Another possible cause is the membrane-level regulation of the functional activity of the enzymes composing the complex.     

In vitro Antiviral Activity of Recombinant Antibodies of IgG and IgA Isotypes to Hemagglutinin of the Influenza A Virus

Seasonal and highly infectious strains of the influenza A and influenza B viruses cause millions of cases of severe complications in elderly people, children, and patients with immune diseases each year. Immunoglobulin A (IgA), which is an active component of humoral immunity, can prevent the spread of the virus in the upper respiratory tract. The preparation and study of the properties of recombinant virus-specific IgA could be an important approach to finding new means of preventing and treating influenza. Based on CHO DG44 cells, we developed stable monoclonal cell lines that produce monomeric and dimeric antibodies FI6-IgA1 and FI6-IgA2m1 to hemagglutinin (HA) of the influenza A virus. When studying the productivity, growth, and stability of the obtained clones, we found that the dimeric form of antibodies of IgA1 isotype is superior to other forms. The dimeric form of IgA antibodies plays a key role in mucosal immunity. Recognizing the prospects of using dimeric IgA as prophylactic and therapeutic mucosal drugs for viral infections, we studied their virus-neutralizing and antiviral activities on MDCK cell culture and compared them with the antibodies of the IgG1 isotype. This study presents the data on antiviral and virus-neutralizing activities of the FI6-IgA1 dimers to seasonal and highly infectious strains of influenza A virus.     

Computer simulation of the preautomatic pause in pacemaker cells of the sinoatrial node

The duration of the preautomatic pause as a function of sinoatrial node, the type of pacemaker cells, acetylcholine concentration, the duration of high-frequency stimulation, and the conductivity of gap junctions has been studied. It was found that the preautomatic pause in peripheral pacemakers occurs at a higher concentration of acetylcholine as compared with central pacemakers. The dependence of the duration of the preautomatic pause on the gap junction conductivity is a nonlinear one.