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Biomedical subjects

M Laskowski

Publications and source records attributed to M Laskowski.

At least 73 records · Page 4Linked to original sources
PubMed1980

A Ser162/Gly162 polymorphism in Japanese quail ovomucoid.

Japanese quail ovomucoid exists in two polymorphic forms. One has serine, the other glycine at position 162. The tryptic peptide corresponding to positions 160 to 164 was purified from ovomucoids isolated from egg whites of eggs laid by 11 different hens and subjected to amino acid analysis. The quantitative distribution of serine and glycine in this pentapeptide is consistent with the interpretation that the ovomucoid gene exists in two codominant allelic forms at one locus. Even though the gene product is apparently expressed only in the female, these results indicate that the ovomucoid structural gene is transmitted as a simple Mendelian character which is neither sex-linked nor shows dominance. Intact third domains (positions 131 to 186) isolated from the two allelic forms of ovomucoid interact with bovine beta-trypsin in a similar but not identical manner; the complex with the glycine form dissociates more rapidly. Evidence is presented which suggests that glycine is the ancestral residue at position 162; yet, the serine form is the more frequent phenotype.

Amino Acids↗
PubMed1979

Accessibility of some regions of DNA in chromatin (chicken erythrocytes) to single strand-specific nucleases.

The susceptibility of the DNA in chromatin to single strand-specific nucleases was examined using nuclease P1, mung bean nuclease, and venom phosphodiesterase. A stage in the reaction exists where the size range of the solubilized products is similar for each of the three nucleases and is nearly independent of incubation time. During this stage, the chromatin fragments sediment in the range of 30 to 100 S and contain duplex DNA ranging from 1 to 10 million daltons. Starting with chromatin depleted of histones H1 and H5 similar fragments are generated. In both cases these nucleoprotein fragments are reduced to nucleosomes and their multimers by micrococcal nuclease. Thus, chromatin contains a limited number of DNA sites which are susceptible to single strand-specific nucleases. These sites occur at intervals of 8 to 80 nucleosomes and are distributed throughout the chromatin. Nucleosome monomers, dimers, or trimers were not observed at any stage of single strand-specific nuclease digestion of nuclei, H1- and H5-depleted chromatin, or micrococcal nuclease-generated oligonucleosomes. Each of the three nucleases converted mononucleosomes (approximately 160 base pairs) to nucleosome cores (approximately 140 base pairs) probably by exonucleolytic action that was facilitated by the prior removal of H1 and H5. The minichromosome of SV40 is highly resistant to digestion by nuclease P1.

Animals↗
PubMed1979

Characterization of the inactive fragment resulting from limited proteolysis of human alpha1-proteinase inhibitor by Crotalus adamanteus proteinase II.

The inactive 50,000-dalton fragment of human plasma alpha1-proteinase inhibitor resulting from limited proteolysis of the inhibitor by Crotalus adamanteus proteinase II has been isolated and partially characterized. The amino acid composition of the inactivated inhibitor indicates the loss of a peptide fragment from the intact inhibitor. Both intact and inactivated inhibitor contain COOH-terminal lysine. However, the NH2 terminus of the intact inhibitor is Glx, whereas that of inactivated inhibitor is methionine. NH2-terminal analysis of the inactive inhibitor fragment revealed the following sequence: -Met-Phe-Leu-Glu-Ala-Ile-Pro-Met-Ser-Ile-Pro-Pro-Gln-Val-Lys-Phe-Asn. The data show that the venom proteinase has inactivated alpha1- proteinase inhibitor by cleavage of a single bond which differs from that reported for trypsin or papain.

Amino Acid Sequence↗
PubMed1978

Specific cleavages inflicted by venom phosphodiesterase on superhelical phiX174 DNA.

A single strand specific endonuclease, venom phosphodiesterase, acting on superhelical phiX174 DNA, inflicts at least seven specific cleavages. Six of these were located to within approximately +/-40 base-pairs by mapping with restriction endonucleases. They are at 12%, 27.4%, 42.7%, 47.5%, 76.1%, and 82.5%. All of these sites lie within regions containing runs of 16 or more base-pairs, of which 12 or more are A and T. Other similarly (A + T)-rich regions in the genome are not cleaved by the enzyme. Increasing the superhelical density of the substrate did not alter the locations of the cleavage sites. There is no correlation between the locations of the cleavage sites and the three known major promoter sites. Only two of five postulated transcription termination sites are cleaved by phosphodiesterase even though all of these terminators contain (A + T)-rich regions. The area containing the origin of viral DNA replication, which includes an (A + T)-rich sequence, is not cleaved.

Coliphages↗
PubMed1978

Purification and some properties of two proteinases from Crotalus adamanteus venom that inactivate human alpha 1-proteinase inhibitor.

Two proteinases (proteinases I and II) have been purified from Crotalus adamanteus venom to the stage of electrophoretic homogeneity and proteinase II has been crystallized. The proteinase differ slightly in molecular weight and amino acid composition. Both are metalloenzymes requiring Zn2+ or Ca2+, or both; neither requires thiol compounds for activation. The proteinases are free of esterolytic activity against benzoly-L-arginine ethyl ester and benzoyl--tyrosine ethyl ester. Proteinase II cleaves the oxidized B chain of insulin at the bonds Phe1-Val2, His5-Leu6, His10-Leu11, Ala14-Leu15, Leu15-Tyr16, and Tyr-16-Leu17. Digestion of polylsine and polyarginine by proteinase II liberates products ranging from dodecapeptides to hexapeptides. Proteinases I and II catalytically inactive human plasma alpha 1-proteinase inhibitor (54,000 daltons). Electrophoretic analysis of the reaction of proteinase II with alpha 1-proteinase inhibitor reveals that an inactivated inhibitor species of 50,000 daltons is formed, and a peptide of 4,000 daltons is released. The gradual disappearance of the native inhibitor results in the corresponding loss of inhibitory activity against trypsin and chymotrypsin.

Amino Acids↗
PubMed1977

An endonuclease activity of venom phosphodiesterase specific for single-stranded and superhelical DNA.

A homogeneous preparation of venom phosphodiesterase from Crotalus adamanteus possesses an intrinsic endonuclease activity, specific for superhelical (form I) and single-stranded DNA. The phosphodiesterase degrades single-stranded T7 DNA by endonucleolytic cleavages. Duplex T7 DNA is hydrolyzed by the liberation of acid-soluble products simultaneously from the 3' and 5' termini but without demonstrable internal scissions in duplex regions. Since venom phosphodiesterase is known to hydrolyze oligonucleotides stepwise from the 3' termini, the cleavage at the 5' end of duplex T7 DNA is ascribed to an endonuclease activity. Form I PM2 DNA is nicked to yield first relaxed circles and then linear DNA which is subsequently hydrolyzed only from the chain termini. The linear duplex DNA intermediates consist of a discrete series of fragments (11 are usually resolved on agarose gels) with initial molecular weights ranging from 6.3 x 10(6) (the intact PM2 DNA size) to approximately 1 x 10(6). The cleavage of the form I molecule must, therefore, occur at a limited number of unique sites. The enzyme also cleaves nonsuperhelical, covalently closed circular PM2 DNA but at a 10(4) times slower rate. Both the endonuclease activity on form I DNA and the known exonuclease activity co-migrate on polyacrtkanude gels, are optimally active at pH 9, are stimulated by small concentrations of Mg2+, and are similarly inactivated by heat, reducing agents, and EDTA.

DNA, Single-Stranded↗