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B Velan

Publications and source records attributed to B Velan.

64 records · Page 4Linked to original sources
PubMed1985

Bovine interferon alpha genes. Structure and expression.

The bovine genome contains a gene family of interferon-alpha s (bIFN-alpha) that consists of at least five distinct members. Four of the bIFN-alpha genes isolated show a high degree of homology (97% in the nucleotide sequence and 93% in amino acid sequence). The overall homology in amino acid sequence of bIFN-alpha to human, murine, and rat IFNs-alpha is approximately 60%. Yet there are amino acid clusters (positions 28-41 and 118-146) which are highly conserved throughout the mammalian evolution and in which the overall homology can be as high as 86%. Within the C terminus conserved cluster there is a sequence containing 9 amino acids completely conserved in 16 mammalian IFNs-alpha and of these, 7 are also shared with a similar domain in some bacterial toxins, implying a common functional role for these domains. One of the genes, IFN-alpha C, was expressed in Escherichia coli. The purified bacterial IFN (specific activity, 2 X 10(8) units/mg) exhibited antiviral activity on bovine cells but no detectable activity was demonstrated on human and simian cells.

Amino Acid Sequence↗
PubMed1985

Cloning, expression and biological activity of a new variant of human interferon alpha identified in virus induced lymphoblastoid cells.

A synthetic oligonucleotide complementary to a highly conserved sequence in the IFN-alpha gene family, was used to screen a Namalva cDNA library. Among the cDNA clones having typical IFN-alpha traits, one was distinct from previously characterized IFN-alpha cDNAs. E. coli cells carrying this recombinant cDNA plasmid express an alpha-interferon activity. The sequence of this IFN-cDNA is extremely homologous (99.5%) to that of the IFN-alpha J gene and is designated IFN-alpha J1. Several E. coli trp expression plasmids were constructed for efficient transcription and translation of the mature IFN-alpha J1. The maximal level of expression (5 X 10(3) molecules/cells) was obtained from plasmid pJ1-4. A synthetic consensus translation initiation sequence coupled to the trp p/o region (in pJ1-5) proved to be 10 times less effective in promoting metIFN production in bacteria, than the in-vitro mutated trpL initiation sequence carried on pJ1-4. The bacterial IFN-alpha J1 was purified (to over 90% purity) to a specific activity of 1.3 X 10(8) units/mg. The antiviral activity of the purified IFN-alpha J1 was compared with other highly purified IFN-alpha species (bacterial IFN alpha A and alpha C, leukocyte IFN-alpha 1, leukocyte IFN mixture and Namalva IFN preparation) on a large panel of mammalian cell cultures. IFN-alpha J1 exhibits a distinct antiviral activity.

Amino Acid Sequence↗
PubMed1985

Cloning of a bovine interferon-alpha gene subfamily and comparisons between genetically engineered and leukocyte bovine interferons.

Bovine peripheral leukocytes were virally induced for interferon production, and an acid stable, SDS stable, antiviral activity was detected in the preparation. This bovine interferon (BoIFN) was tested for its ability to induce an antiviral state in various mammalian cells and was found to be specific to cells from bovine origin. The BoIFN cross reacts with antibodies against human IFN-alpha but these antibodies do not neutralize the bovine IFN activity. Leukocyte BoIFN exhibits polymorphism upon Affi-Gel Blue chromatography and SDS-PAGE (16k and 24K). The virally induced leukocytes produce a 13S mRNA which upon translation in oocytes yields an active IFN molecule. Bovine genomic library was constructed and screened for BoIFN-alpha sequences, using human IFN-alpha probes. From the clones isolated, five were found to represent distinct genes. Sequence analysis indicate that these genes are closely related (94% homology). One of these genes was expressed in E. coli under the control of trp promoter operator. The physicochemical and biological properties of the bacterial BoIFN-alpha product resemble those of a subpopulation of natural BoIFN.

Animals↗
PubMed1984

Mutations not altering the symmetrical sequences in the trp operator yield a constitutive phenotype.

An E. coli trp promoter operator mutant was constructed, having two base pair alterations at position -4 and -1 relative to the transcription initiation site (+1). Expression of chloramphenicol acetyltransferase gene under this trp promoter operator suggests that it is almost fully constitutive. This trp Oc in vitro derived mutant differs from previously isolated Oc mutants in that its twofold symmetry sequence is identical to that of the wild type trp operator. The base substitution in the operator does not affect the functionality of the trp promoter. The trp Oc promoter DNA fragment is engineered so that it can be manipulated conveniently for efficient expression of various genes in E. coli.

Acetyltransferases↗
PubMed1981

Mouse beta 2-microglobulin cDNA clones: a screening procedure for cDNA clones corresponding to rare mRNAs.

We have isolated three cDNA clones for beta 2-microglobulin, the small subunit of the major histocompatibility antigens. beta 2-Microglobulin makes up less than 0.1% of mouse liver protein, and its mRNA is approximately 0.03% of liver poly(A)+ mRNA. The cDNA clones were identified by screening 1400 cDNA clones made from 9--10S mouse liver poly(A)+ mRNA. The procedure for screening the cDNA clones involved binding pooled plasmid DNA to nitrocellulose filters and testing the ability of each filter to select beta 2-microglobulin mRNA. The filter-selected mRNAs were assayed for their ability to direct the synthesis of beta 2-microglobulin in translation reactions in vitro. The isolated clones were shown by nucleotide sequence analysis to encode beta 2-microglobulin. The positive-selection--hybridization assay has been modified to facilitate the screening of large numbers of cDNA clones, and the modified assay should allow the isolation of cDNAs corresponding to any mRNA whose in vitro translation products can be immunoprecipitated. These modifications are of particular value in the isolation of cDNA clones corresponding to rare species of mRNA.

Amino Acid Sequence↗
PubMed1977

Rapid identification and quantitation of small numbers of microorganisms by a chemiluminescent immunoreaction.

A method (patent pending) for rapidly identifying and quantitating small numbers of microorganisms was developed based on the specific immunoreaction of microorganisms with homologous antibodies linked by conjugation to peroxidase. The high sensitivity of the method is due to the use of a chemiluminescent reaction for the determination of the enzyme. The reaction was performed on Alcar supports with low nonspecific adsorption. The very low noise achieved permitted the detection of as few as 30 to 300 bacterial cells.

Bacteria↗