[Forms of LonB protease from Archaeoglobus fulgidus devoid of the transmembrane domain: the contribution of the quaternary structure to the regulation of enzyme proteolytic activity].

Deletion of the transmembrane domain (TM-domain) of Archaeoglobus flggidus LonB protease (AfLon) was shown to result in uncontrollable activation of the enzyme proteolytic site and in vivo autolysis yielding a stable and functionally inactive fragment consisting of both alpha-helical and proteolytic domains (alphaP). The deltaTM-AfLonTM-S590A enzyme form, obtained by site-directed mutagenesis of the catalytic Ser residue, is capable of recombination with the alphaP fragment. The mixed oligomers were shown to be proteolytically active, which indicates a crucial role of subunit interactions in the activation of the AfLon proteolytic site. The thermophilic nature of AfLon protease was found to be due to the special features of the enzyme activity regulation, the structure of ATPase domain, and the quaternary structure.

[Structure-activity analysis of ribonuclease A and related proteins]. / Strukturno-funktsional'nyi analiz ribonukleazy A i rodstvennykh belkov.

A detailed analysis of noncovalent interactions in the RNase A molecule was carried out. For this purpose, contact maps based on structural data were constructed. Three hydrophobic nuclei and five microclusters were identified, and their quantitative parameters were calculated. The contacts between amino acid residues of the active center and the hydrophobic nuclei were established. The distribution of the charged amino acid residues on the of RNase A surface was shown. The data obtained was discussed in the context of the ribonuclease A family. The substitutions seen from the alignment of amino acid sequences in the family might have influence on the spatial structure of different parts of RNase A and their mutual orientation and, consequently on the biological activity of family members.