[Molecular evolution of intracellular Ca2+-dependent proteases].

The structural features and evolutionary interrelationships of the intracellular Ca2+-dependent cysteine enzymes calpains, proteases of the family C2 (EC 3.4.22.17), are considered. A variety of identified sequences of calpains and calpain-like polypeptides found in organisms of different taxons, from the simplest to mammals, are described. Calpains of the major evolutionary groups, typical and atypical, are classified by the analysis of their phylogenetic tree and are differentiated due to the presence of the calmodulin-like Ca2+-binding domain. It is shown that, along with enzymes having "advanced" characteristics (heterodimeric structure, presence of tissue-specific isoforms and splice variants, regulation by the endogenous inhibitor calpastatin, and others), higher organisms contain homologues of calpains of lower eukaryotes. A high degree of homology of the catalytic domain of calpains and the variable structure of other functional domains indicate that calpains are implicated in various physiological processes with the retention of their regulatory role.

[To the problem of proteolytic enzyme evolution].

Own and literature data on putative evolution of proteolytic enzymes have been reviewed. Modern principles of peptidase classification based on evaluation of homology of more than 66 thousand gene sequences and similarity of general structural organization of almost 2.5 thousands of known enzymes are considered. The review highlights not only evolutionary interrelationships inside related peptidase families, their possible evolutionary background, but also evolutionary determined differences in certain proteolytic pathway in organisms belonging to different taxons.

[Formation of immune proteasomes and development of the immune system in mammalian ontogenesis].

Current concepts of the structure of immune proteasomes and their role in immune response have been considered. The main attention has been paid to the formation of immune proteasomes in secondary lymphoid and nonlymphoid organs during ontogenesis of mammals. The causes of ineffective formation of immune system in early postnatal development have been discussed.

Peculiarities of proteasome pool formation in rat spleen and liver during postnatal development.

Changes in the specific activity and amounts of 26S and 20S proteasome pools in rat spleen and liver during postnatal development and appearance in them of immune subunits were studied. Two decreases in chymotrypsin-like activity of the proteasome pools were recorded during the first three weeks after birth. The activity minimum fell on the 11th and 19th days, and the first decrease was more prolonged and pronounced than the second. The decrease in the specific activity of the 26S proteasome pools was associated with a reduction of their quantity. The 20S proteasome pools displayed no such decreases. Noticeable quantities of immune subunits LMP7 and LMP2 were revealed by Western blotting in the spleen on the 7th day and on the 19th day in the liver, concurrently with the beginning of the decrease in the proteasome activity. It was concluded that during the first three weeks of postnatal development the proteasome pools in rat spleen and liver were replaced twice, and in the spleen (a lymphoid organ) a qualitatively new pool containing immune subunits appeared nearly two weeks earlier than in the liver (a non-lymphoid organ). The appearance of immune proteasomes in different organs and tissues during some weeks after birth seems to explain the immune system inefficiency during embryogenesis and early postnatal development.

Correlation of intracellular Ca(2+)-activated proteinase activity and cholesterol content in white sea mussel (Mytilus edulis) membranes at different water saltiness.

Correlation between changes in activity of intracellular Ca(2+)-activated proteinases and cholesterol content in mussels in response to changes in habitat saltiness was detected in mollusks from littoral and sublittoral White sea zones. Calpain activity in mussels decreased in low water saltiness and increased in high saltiness in parallel with decrease in cholesterol content, which attests to decreased microviscosity and modification of permeability of biomembranes. A complex pattern of interactions between metabolic routes in mussels under conditions of different habitat saltiness was detected.

[Effect of dietary intoxication by mercury salts on cysteine proteinase activity in rat tissues]. / Vliianie pishchevoi intoksikatsii soliami rtuti na aktivnost' tsisteinovykh proteinaz v tkaniakh krys.

The experiments on dietary intoxication of rats by HgI2 or Hg(NO3)2 show that the activities of lysosomal proteinase cathepsin B and cytosolic Ca(2+)-activated proteinases (calpains I and II) in the liver and kidney depend on the mercury salt solubility and the exposure duration. Mercury iodide and nitrate contribute more to inhibiting cathepsin B and calpains activities in the above tissues, respectively.

Efficient templates for Q beta replicase are formed by recombination from heterologous sequences.

A very efficient replicase template has been isolated from the products of spontaneous RNA synthesis in an in vitro Q beta replicase reaction that was incubated in the absence of added RNA. This template was named RQ135 RNA because it is 135 nucleotides in length. Its sequence consists entirely of segments that are homologous to ribosomal 23 S RNA and the phage lambda origin of replication. The sequence segments are unrelated to the sequence of Q beta bacteriophage genomic RNA. Nonetheless, this natural recombinant is replicated in vitro at a rate equal to the most efficient of the known Q beta RNA variants. Apparently, the structural properties that ensure recognition of an RNA template by Q beta replicase are not confined to viral RNA, but can appear as a result of recombination among other RNAs that usually occur in cells.