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Polypeptide toxin pi-AnmTX Hcr 1b-1 with a molecular weight 4537 Da was isolated from the whole body extract of sea anemone by a multistage liquid chromatography. The BLAST search algorithm revealed homology of the novel toxin amino acid sequence to the group of the known sea anemone toxins including BDS and APETx with similarity less then 50%. The toxin pi-AnmTX Hcr 1b-1 inhibited the amplitude of the fast component of integral ASIC3 current in electrophysiological studies on receptors expressed in Xenopus laevis oocytes. The calculated IC50 value was 5.5 +/- 1.0 microM. Among the known polypeptide toxins interacted with ASICs channels, the micro-AnmTX Hcr 1b-1 toxin is the least potent inhibitor that in our opinion correlates with a small amount of charged amino acid residues in its structure.

Using methods of molecular biology we defined the structures of the 31 sea anemone Heteractis crispa genes encoding polypeptides which are structurally homologous to the Kunitz proteinase inhibitor family. Identified amino acid sequences have point residue substitutions, high degree of homology with sequences of known H. crispa Kunitz family members, and represent a combinatorial library of polypeptides. We generated their three-dimensional structures by homologous modeling methods. Analysis of their molecular electrostatic potential enabled us to divide given polypeptides into three clusters. One of them includes polypeptides APHC1, APHC2 and APHC3, which were earlier shown to possess a unique property of inhibiting of the pain vanilloid receptor TRPV1 in vitro and providing the analgesic effects in vivo in addition to their trypsin inhibitory activity. Molecular docking made possible establishing the spatial structure of the complexes, the nature of the polypeptides binding with TRPV1, as well as functionally important structural elements involved in the complex formation. Structural models have enabled us to propose a hypothesis contributing to understanding the APHC1-3 impact mechanism for the pain signals transduction by TRPV1: apparently, there is an increase of the receptor relaxation time resulted in binding of its two chains with the polypeptide molecule, which disrupt the functioning of the TRPV1 and leads to partial inhibition of signal transduction in electrophysiological experiments.

The influence of different environmental values of the pH and temperature on the spatial organization of serine proteinase inhibitor from the sea anemone Heteractis crispa (=Radianthus macrodactylus) on the level of tertiary and secondary structure was studied by CD spectroscopy. The molecule InhVJ was shown to possess a high conformational thermo- and pH-stability. We determined the point of conformational thermotransition of polypeptide (70 degrees C) after which the molecule gets denaturational stable state with conservation of 80% proteinase inhibitory activity. The significant partial reversible changes of molecule spatial organization were established to occur at the level of tertiary structure in the process of acid-base titration in the range of pH 11.0-13.0. This can be explained by of ionization of tyrosine residues. The molecule InhVJ is conformationally stable at the low pH values (2.0). The quenching of tyrosine residues by acrylamide showed that two of these residues are accessible to the quencher in full, while the third part is available.

A serine protease inhibitor with a molecular mass of 6106 +/- 2Da (designated as InhVJ) was isolated from the tropical anemone Radianthus macrodactylus by a combination of liquid chromatography methods. The molecule of InhVJ consists of 57 amino acid residues, has three disulfide bonds, and contains no Met or Trp residues. The N-terminal amino acid sequence of the inhibitor (19 aa residues) was established. It was shown that this fragment has a high degree of homology with the N-terminal amino acid sequences of serine protease inhibitors from other anemone species, reptiles, and mammals. The spatial organization of the inhibitor at the levels of tertiary and secondary structures was studied by the methods of UV and CD spectroscopy. The specific and molar absorption coefficients of InhVJ were determined. The percentage of canonical secondary structure elements in the polypeptide was calculated. The inhibitor has a highly ordered tertiary structure and belongs to mixed alpha/beta or alpha + beta polypeptides. It was established that InhVJ is highly specific toward trypsin (Ki 2.49 x 10(-9) M) and alpha-chymotrypsin (Ki 2.17 x 10(-8) M) and does not inhibit other proteases, such as thrombin, kallikrein, and papain. The inhibitor InhVJ was assigned to the family of the Kunitz inhibitor according to its physicochemical properties.

The interaction of inhibitor VJ (InhVJ), isolated from sea anemone R. macrodactylus, with different proteases was investigated. The following enzymes were tested: serine proteases (trypsin, alpha-chymotrypsin, plasmin, thrombin, kallikrein), cysteine protease (papain) and aspartic protease (pepsin). Inhibitor VJ interacted only with trypsin and 6-chymotrypsin. Kinetic and thermodynamics parameters of intermolecular complexes formation were determined: KD = 7,38 x 10(-8) M and 9,93 x 10(-7) M for pairs InhVJ/trypsin and InhVJ/alpha-chymotrypsin, respectively.

Partial amino acid sequences of the actinoporins Or-A (136 aa) and Or-G (144 aa) isolated from the Sea of Japan sea anemone Oulactis orientalis were determined by sequencing the clones obtained by the amplification of genomic DNA and cDNA with specific primers to the N-terminal regions of the 0. orientalis actinoporin sequences and to the C-terminal region, which is known to be highly conservative in all the known actinoporin sequences. The complete structures of Or-A (165 aa) and Or-G (173 aa) were established by sequencing the cDNA clones obtained by the fast amplification of 3'-ends of cDNA. A comparative analysis of the amino acid sequences of the Oulactis actinoporins with those of actinoporins from tropical species revealed considerable differences in the structures of their N-terminal fragments and their membrane-binding sites. We believe that these differences could explain lower hemolytic activities of Or-A and Or-G than that of actinoporins from the tropical species.

Three cytolytic toxins (RTX: RTX-A, RTX-S, and RTX-G) were isolated from the sea anemone Radianthus macrodactylus and characterized. The purification scheme involved hydrophobic chromatography on Polychrom-1, batch-chromatography on CM-23 cellulose, gel filtration on Akrilex P-4, cation-exchange chromatography on CM-32 cellulose, and HPLC on an ion-exchange Ultropac TSK CM-3SW column and a reversed-phase Silasorb C18 column. The molecular masses of RTXs (ca. 20 kDa) were determined by SDS-PAGE in a density gradient of PAG. They are highly basic polypeptides (pI of 9.8 for RTX-A and RTX-S and 10.5 for RTX-G) containing similar amino acid compositions with a high content of basic and hydrophobic residues and the absence of Cys residues. The hemolytic activities of RTX-A, RTX-S, and RTX-G were determined to be 3.5, 5.0, and 1.0 x 10(4) HU/mg, respectively. Exogenous sphingomyelin inhibits their action on the erythrocyte membrane. The N-terminal sequence of RTX-A was determined to be ALAGAIIAGAGL/KGLKI/FLIEVLGEG--V/NKVKI-.

Two low-molecular cytolytic toxins (RmI and RmII) and four trypsin inhibitors were isolated from the aqueous extract of sea anemone Radianthus macrodactylus. The method of isolation involved precipitation with acetone, gel filtration on acrylex P-4, ion-exchange chromatography on CM-32 cellulose, affinity chromatography on trypsin-binding sepharose 4B, ion exchange chromatography on an Ultrapore TSK CM-3SW column, and reversed phase HPLC on a Silasorb C18 column. RmI, RmII, and JnI inhibitor displayed molecular masses 5100, 6100, and 7100 Da, respectively, when subjected to SDS-PAGE. The isoelectric points were 9.2 and 9.3 for RmI and RmII, respectively. The amino acid composition and N-terminal amino acid residue (glycine) were determined for RmI, RmII, and JnI. Both proteins were nontoxic to mice and crabs. Hemolytic activity was determined to be 25 and 20 HU/mg for RmI and RmII, respectively, and their action on erythrocyte membrane was not inhibited by exogenous sphingomyelin. RmI and RmII exhibited antihistamine activity.