A Study of the Structure of Trypsin-Like Serine Proteinases. 2. A Study of Tryptophan Fluorescence in Variants of Miniplasminogen with an Altered Primary Structure

Biophysics - Abstract—Variants of miniplasminogen with an altered primary structure have been designed to study previously described changes in tryptophan fluorescence during plasminogen...     

New producers of site-specific endonucleases from microorganisms of the Bacillus genus

52 strains of Bacillus generum have been tested for production of site-specific endonucleases. The sequence recognized by the enzyme was determined for 23 enzymes, the cleavage site inside the sequence was determined for 5 enzymes. All the enzymes under study were found to be isomers of the known enzymes. The selected strains are peculiar for the high level of site-specific endonucleases content and may be used as producents of the enzymes.     

Expression of a deleted variant of human plasminogen in <Emphasis Type="Italic">Escherichia coli</Emphasis>

A recombinant plasmid carrying a modified gene of human plasminogen (mini-plasminogen), lacking four kringle domains and an amino terminal fragment, and containing an additional oligopeptide of six N-terminal histidine residues has been constructed. The plasmid was used for transformation of E. coli JM 109 cells to obtain a strain producing a recombinant modified human plasminogen. The target protein is superexpressed in a form of inclusion bodies and is composed of more than 50% insoluble protein. The renaturated and chromatographically purified protein exhibits amidolytic activity specific for plasminogen proenzyme in a fibrinolytic system.     

A Study of the Structure of Trypsin-Like Serine Proteinases: 1. Study of Mini-Plasminogen Activation Using Tryptophan Fluorescence

Biophysics - Abstract—It has been shown that the curve of the time dependence of tryptophan fluorescence during plasminogen activation by urokinase is well correlated with kinetic curves of...     

Total RNA suitable for molecular biology analysis

Development of methods based on determining expression of individual genes resulted in the need for large amounts of high quality RNA preparations. It is widely accepted that in intact rRNA the 28S and 18S band ratio must be 2:1. It is not quite clear what is the main cause of lower rRNA bands intensity ratio. It is difficult to isolate RNA with 2:1 28S/18S ratio from RNase-rich and some tumor tissues. At the same time this requirement may be excessive and RNA preparations with lower 28S/18S rRNA ratio may be quite adequate for most techniques of determining gene expression. As demonstrated in this study, the level of a particular RNA may be reliably determined by RT-PCR even in a total RNA that is usually considered as degraded (28S to 18S ratio as low as 0.4), provided that random primer is used in RT. In contrast, the use of the oligo(dT) primer in RT-PCR may lead to underestimation of specific mRNA level in the degraded RNA samples, depending on the distance of amplified fragment from the poly(A) end. A criterion based on average degradation level of a number of reference genes is suggested to discriminate specific RNA degradation from random and unspecific ones.     

Restriction endonucleases from Bifidobacteria

The sitespecific restriction endonucleases were found in four strains among the twelve strains of anaerobic bacteria of generum Bifidobacterium. Two of the restriction endonucleases studied, BadI from B. adolescentis LVA1 and BbfI from B. bifidum LVA3, are isoshizomers of XhoI and recognize the nucleotide sequence CTCGAG. The restriction endonucleases Bbf7411I from B. bifidum 7411 and Bla7920I from B. lactentis 7920 recognize and hydrolize the nucleotide sequence TCCGGA having the specifity analogous to the one of restriction endonuclease CauB3I. Like CauB3I, these restriction endonucleases are unable to hydrolyize DNA if the adenine residues in the recognition site are methylated.     

In vitro selection of single-stranded DNA aptamers that bind human pro-urokinase

Single-chain pro-urokinase is an inactive proenzyme form of human urokinase (urinary plasminogen activator) with a Mr of 50,000 which is converted to the active two-chain form by catalytic amounts of plasmin. It is used for thrombolytic therapy of acute myocardial infarction and acute ischemic stroke. We have isolated single-stranded DNA molecules with significantly increased binding affinity for human pro-urokinase by SELEX (systematic evolution of ligands by exponential enrichment) procedure from a pool of 10(15) molecules containing 24 randomized positions which are flanked by defined regions. ssDNA from this library was hybridized with helper "fixture", thus allowing the central random chain to fold into complex three-dimentional shapes. Sequencing data from pro-urokinase aptamers obtained after 12 selection cycles displayed a highly conserved 12-14 base region.