Ignacy Z. Siemion

TUFTSIN : ON THE 30-YEAR ANNIVERSARY OF VICTOR NAJJAR'S DISCOVERY

After a short description of the results of Victor Najjars research on tuftsin and of the discoveries done by other authors in the early stage of tuftsin investigation, the current state of work on tuftsin is presented, based mainly on the literature published in the years 1984-1997. The presentation follows this order: the occurrence of tuftsin and retro-tuftsin sequences in proteins, their synthesis and biology, the antigenic properties of tuftsin, its influence on phagocytic cells, and other biologic activities of tuftsin, including antimicrobial, antiviral, antitumor and central effects, and the search for tuftsin superactive analogs.

Cyclolinopeptide A (CLA) mediates its immunosuppressive activity through cyclophilin-dependent calcineurin inactivation

The immunosuppressive cyclic nonapeptide cyclolinopeptide A inhibits calcium‐dependent, but not calcium‐independent, activation of T lymphocytes comparably to the actions of cyclosporin A and FK506. The concentration required for complete inhibition, however, is 10 times higher than that of cyclosporin A. In addition, we demonstrate that calcineurin, a phosphatase which plays an important role in T lymphocyte signalling, is inhibited in vitro by cyclolinopeptide A by a mechanism dependent on the peptidyl‐prolyl cis‐trans isomerase (PPIase) cyclophilin A but not FKBP12. Direct binding of cyclolinopeptide A to cyclophilin A was confirmed using tryptophan fluorescence studies and PPIase assays. These results represent a third example of the production of a natural product that neutralises calcineurin by a mechanism dependent on the primary binding to a PPIase.

Copper (II) interaction with proline-containing tetrapeptides

Abstract The Cu(II) interactions with four tetrapeptides: Ala-Ala-Ala-Ala, Ala-Ala-Ala-Pro, Ala-Ala-Pro-Ala, and Pro-Ala-Ala-Ala were studied by the absorption, circular dichroism, and electron paramagnetic resonance spectra. The results clearly show that proline residue is a specific structural factor in the formed complexes and, on the other hand, it is a break point in the metal ion coordination to the consecutive peptide bond nitrogens. The only position of proline residue ina peptide sequence that makes proline nitrogen available for the metal ion coordination is the N-terminal position. But even in this case (i.e., in the Cu(II) Pro-Ala-Ala-Ala system) proline plays a critical role in the creation of the specific structures in the complex formed in solution.

Immunoregulatory properties of synthetic peptides, fragments of a proline-rich polypeptide (PRP) from ovine colostrum

It has been previously found that a proline-rich polypeptide (PRP) isolated from ovine colostrum has a regulatory effect on the immune response. A nonapeptide fragment Val-Glu-Ser-Tyr-Val-Pro-Leu-Phe-Pro was isolated from the chymotryptic digest of PRP. The nonapeptide showed biological activity similar to PRP. The determined amino acid sequence was now confirmed by synthesis. Synthetic nonapeptide as well as its C-terminal hexapeptide, Tyr-Val-Pro-Leu-Phe-Pro, showed biological activity similar to PRP and the nonapeptide obtained from PRP.

Immunosuppressive activity in the series of cycloamanide peptides from mushrooms

The immunosuppressor activity of the cycloamanides A, B, C, and D, and two of their D-amino acid residue-containing analogues, was examined using PFC (plaque forming cell) and DTH (delayed type hypersensitivity) tests. It was found that cycloamanide A (CyA A, II) [c-(Phe-Phe-Ala-Gly-Pro-Val-)] and its D-Phe-containing analogue III [c-(Phe-D-Phe-Ala-Gly-Pro-Val-)] are the most potent immunosuppressors of the whole series. The retroanalogue of III [c-(D-Phe-Val-Pro-Gly-Ala-)] was found to be less active than III. The immunosuppressor activity of O-carboxymethyl-Tyr6-antamanide (I) was also tested. It was found that the substitution of one of the Phe residues of ANT by O-carboxymethyl-Tyr does not substantially affect the immunosuppressor activity.

Immunological properties of the thymopentin-like fragments of HLA-DQ

Class II human leukocyte antigens (HLA-II) are cell surface alpha beta heterodimers (M(r) approximately 60,000) that play a pivotal role in the immune response by presenting peptides derived from environmental antigens to the T-cell receptor. A 167-171 fragment of the beta 2-chain of the HLA-DQ molecule consists of the sequence RGDVY, which is very similar to thymopentin (pentapeptide RKDVY, an active fragment (32-36) of thymopoietin, an immune system activator produced in thymi), and at the same time contains the RGD sequence, known as an inhibitor of adhesion processes. We synthesized and investigated the immunomodulatory activity of series of peptide fragments of HLA-DQ containing thymopentin-like sequences. The results indicate that all synthesized peptides suppress the cellular immune response. However, RGDV, RGDVY and QRGDVY show very weak stimulatory activity in humoral immunological response tests. In contrast to the shorter peptides, the nonapeptide fragment of HLA-DQ, TPQRGDVYT, shows significant immunosuppressive activity in all tests. A possible role of these fragments of the polypeptide chain of HLA-DQ in the regulation of HLA functions is discussed.

The informational context of the third base in amino acid codons.

It is shown that in the pairs of amino acids coded by the codons possesing identical bases in the first and second positions, the amino acids with R in the third position are of higher structural importance (which is reflected by higher values of (P alpha + P beta) sums of Chou-Fasman conformational parameters), and of stronger helix forming potentials (reflected by the differences (P alpha - P beta)), than the amino acids coded with Y. The same structural factors seem to be of importance for the codon choice in the case of amino acids coded by more than two codons. The amino acids which prefer alpha-helical over the beta-sheet conformation favour the codons with R in their third position, and those which favour the beta-sheet conformation favour the codons with Y in this position.

The problem of amino acid complementarity and antisense peptides.

The review presents three hypotheses concerning the amino acid complementarity: 1) the Mekler-Blalock antisense hypothesis; 2) the Root-Bernstein approach based on stereochemical complementarity of amino acids and anti-amino acids coded by anticodons read in parallel with the coding DNA strand; 3) Siemion hypothesis resulting from the periodicity of the genetic code. The current state of knowledge as well as the results of the implementations of these hypotheses are compared. A special attention is given to Root-Bernstein and Siemion hypotheses, which differ in only few points of the complementarity prediction. We describe methods of investigation of peptide-antipeptide pairing, including circular dichroism, mass spectrometry, affinity chromatography and other techniques. The biological applications of complementarity principle are considered, such as search for bioeffector-bioreceptor interaction systems, the influence of peptide-antipeptide pairing on the activity of peptide hormones, and the application of antipeptides in immunochemistry. The possible role of amino acid-anti-amino acid interactions in the formation of the spatial structures of peptides, proteins and protein complexes is discussed. Such problems as the pairing preferences of protein-protein interfaces, the role of the pairing in the creation of disulfide bonds and the possible appearance of such interactions in beta-structure are also examined. The main intention of the paper is to bring the complementarity problem to the attention of the scientific community, as a possible tool in proteomics, molecular design and molecular recognition.

To the problem of biologically active conformation of enkephalin

SummaryA semi-rigid structural analog of [Leu5] enkephalin, possessing the azo-bridge between Tyr1 and Phe4 residues, was synthesized, along with two other linear enkephalin analogs: [4′-amino Phe4] enkephalin and [4′hydroxyphenyl/-azo Phe4] enkephalin. The results of the determination of the analgesic activity of the synthesized compounds suggest that the biologically active conformation of the enkephalin molecule should be such that both aromatic rings, Tyr1 and Phe4, are situated in close proximity.

Immunosuppressive activity of hymenistatin I.

Hymenistatin I (HS-I), a cyclic octapeptide [c-(-Pro-Pro-Tyr-Val-Pro-Leu-Ile-Ile-)], was synthesized by the solid-phase peptide synthesis method and examined for its immunosuppressive activity in the humoral and cellular immune responses. The peptide activity was tested on cell lines producing various cytokines. The results are compared with the activity of the well-known immunosuppressive agent cyclosporin A (CsA). It was found that hymenistatin I exerts immunosuppressive effect (both in the humoral and cellular immune responses) comparable with that of CsA. Comparison of the influence of HS-I and CsA on cytokines production suggests that the mechanisms of the interaction with the immunological system are substantially different for the two compounds tested.