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J Leluk

Publications and source records attributed to J Leluk.

11 recordsLinked to original sources
PubMed2001

Application of genetic semihomology algorithm to theoretical studies on various protein families.

Several protein families of different nature were studied for genetic relationship, correct alignment at non-homologous fragments, optimal sequence consensus construction, and confirmation of their actual relevance. A comparison of the genetic semihomology approach with statistical approaches indicates a high accuracy and cognition significance of the former. This is particularly pronounced in the study of related proteins that show a low degree of homology. The sequence multiple alignments were verified and corrected with respect to the questionable, non-homologous fragments. The verified alignments were the basis for consensus sequence formation. The frequency of six-codon amino acids occurrence versus position variability was studied and their possible role in amino acid mutational exchange at variable positions is discussed.

Algorithms↗
PubMed2000

Regularities in mutational variability in selected protein families and the Markovian model of amino acid replacement.

Three families of proteinase inhibitors and the trypsin family were the subjects of the analysis of amino acid replacements at aligned positions. This approach concerned some specific types of replacement and the mechanisms that can be involved in their control. The usefulness of the Markovian model for interpretation of mutational replacement within homologous proteins was examined. The same sequences were also analyzed with the use of the non-Markovian algorithm of genetic semihomology. This study leads to the conclusion that the Markovian model is not suitable for the interpretation of protein mutational variability since: (1) The information about the history of a variable unit is included in its genetic code. (2) This information plays an important role in the probability of further possible changes of the unit.

Algorithms↗
PubMed1998

A new algorithm for analysis of the homology in protein primary structure.

A new algorithm for analysis of the homology and genetic semihomology in protein sequence is described. It assumes the close relation between the compared amino acids and their codons in related proteins. The algorithm is based on the network of the genetic relationship between amino acids and, thus differs from the commonly used statistical matrices. The results obtained by using this method are more comprehensive than used at present, and reflect the actual mechanism of protein differentiation and evolution. They concern: (1) location of homologous and semihomologous sites in compared proteins; (2) precise estimation of insertion/deletion gaps in non-homologous fragments; (3) analysis of internal homology and semihomology; (4) precise location of domains in multidomain proteins; (5) estimation of genetic code of non-homologous fragments; (6) construction of genetic probes; (7) studies on differentiation processes among related proteins; (8) estimation of the degree of relationship among related proteins; (9) studies on the evolution mechanism within homologous protein families and (10) confirmation of actual relationship of sequences showing low degree of homology.

Algorithms↗
PubMed1989

Comparative studies on the protein composition of hymenopteran venom reservoirs.

The proteins of venom reservoirs from 25 hymenopteran species from 21 genera were investigated with regard to their protein composition and immunological similarities. It was found that low mol. wt proteins and polypeptides are typical for the venoms of ants, social wasps and bees. Six species of ichneumonoid parasitic wasps lack these low mol. wt proteins. Except for bee venoms none of the low mol. wt proteins contain mannose. The venoms of ichneumonoid parasites and ants contained primarily acidic proteins, whereas those of social wasps and bees contained abundant neutral and basic proteins. Immunological analysis showed that a number of venom proteins from parasitic braconid (Chelonus) wasps shared conserved immunoreactive determinants with the venom proteins of higher Hymenoptera, including some not of parasitic habit. Implications of phylogenetic relationships among hymenopteran species are discussed.

Animals↗
PubMed1985

The squash family of serine proteinase inhibitors. Amino acid sequences and association equilibrium constants of inhibitors from squash, summer squash, zucchini, and cucumber seeds.

Six amino acid sequences for trypsin inhibitors isolated from squash, summer squash, zucchini, and cucumber seeds were determined. All these inhibitors along with the two previously sequenced squash inhibitors (1) form the squash inhibitor family. The striking characteristic of the family is that its member inhibitors are very small (29-32 residues, 3 disulfide bridges). The association equilibrium constants with bovine beta trypsin for 6 squash family inhibitors were determined and range from 5.9 X 10(10) to 9.5 X 10(11) M-1.

Amino Acid Sequence↗
PubMed1985

Purification and characterization of the trypsin inhibitor from Cucurbita pepo var. patissonina fruits.

Three trypsin inhibitor fractions were found in white bush fruits (Cucurbita pepo L. var. patissonina). One of them, CPPTI-fIII, was purified to homogeneity by means of affinity and ion exchange chromatography. It is a cysteine-poor protein with an approximate Mr of 21 000. The inhibitor contains arginine at position P1 of the reactive site and inhibits bovine trypsin, hog pancreatic kallikrein and subtilisin. This inhibitor differs from the inhibitors of white bush dormant seeds, CPPTI-I and CPPTI-II, in its amino-acid composition, molecular mass, amino-acid residue at position P1 of the reactive site and inhibition spectrum.

Amino Acids↗
PubMed1985

Isolation of two trypsin inhibitors from resting seeds of the white bush (Cucurbita pepo var. patissonina) and their properties.

Two trypsin inhibitors, CPPTI-I and CPPTI-II of Mr 3 250 and 7 850, respectively, were isolated from resting white bush seeds. Both inhibitors are cysteine-rich proteins. In addition to trypsin, they inhibit a trypsin-like enzyme isolated from Streptomyces griseus proteinase but they do not act on chymotrypsin, kallikrein or subtilopeptidase A. The isolated inhibitors contain a lysine residue in position P1 of the reactive site.

Amino Acids↗
PubMed1984

Trypsin inhibitors in summer squash (Cucurbita pepo) seeds. Isolation, purification and partial characterization of three inhibitors.

Three trypsin inhibitors were isolated from summer squash (Cucurbita pepo) seeds and purified to homogeneity by fractionation with ammonium sulphate and methanol, ion-exchange chromatography and gel filtration. All three inhibitors have lysine at their active site. Two of them (II, IV) show the same isoelectric point (at pH 5.6), amino acid composition and molecular mass (3259). The third inhibitor (III) of molecular mass of 3654 and isoelectric point at 4.9 has additionally one histidine residue and two glutamic acid residues more per molecule.

Amino Acids↗
PubMed1983

Preparation and characteristics of trypsin inhibitors from the seeds of squash (Cucurbita maxima) and zucchini (Cucurbita pepo var. Giromontia).

One trypsin inhibitor (I) from zucchini seeds and two (I and III) from squash seeds were isolated by ammonium sulphate salting out and chromatography on SP-Sephadex C-25 and immobilized trypsin. The inhibitors have the same molecular mass, about 3300, contain 29 amino acids, have three disulphide bridges, and lack Thr, Phe and Trp. The isoelectric point of the zucchini inhibitor I and squash inhibitor I is of 5.6, whereas that of the squash inhibitor III--of 8.3. Arg is the N-terminal amino acid of all three inhibitors. On modification of the Arg residues with 1,2-cyclohexanedione both squash inhibitors become inactivated. The zucchini inhibitor I becomes inactivated on acetylation of free amino groups. In all three inhibitors, on enzymatic modification with trypsin at pH 3.2, Ile appears as a new N-terminal amino acid. On this basis it can be supposed that Arg-Ile form the reactive site of the trypsin inhibitors from squash seeds, and Lys-Ile of the zucchini seed inhibitor.

Amino Acids↗
PubMedDate not supplied

A non-statistical approach to protein mutational variability.

The non-statistical, non-Markovian model of protein mutational variability is described. There are presented the essential features of the algorithm of genetic semihomology and some examples of its application. The results of genetic semihomology approach are compared with the results obtained by using statistical algorithms and matrices which are assumed in widely used programs such as ClustalW, FASTA, MultAlin and BLAST. The aim of the new algorithm elaboration is to improve the accuracy of the results of protein sequence comparison, avoid the wrong assumptions and misinterpretation of the results, and increase the amount of information available from such study.

Amino Acid Sequence↗