PubMed Health⌕ Search

Biomedical subjects

M S Urdea

Publications and source records attributed to M S Urdea.

8 recordsLinked to original sources
PubMed1992

At least five related, but distinct, hepatitis C viral genotypes exist.

Hepatitis C virus, the major causative agent of blood-borne non-A, non-B hepatitis in the world, has been the subject of considerable nucleic acid sequence analysis. Although all reported hepatitis C sequences from the United States have been represented by the prototype hepatitis C virus type 1 sequence, two groups of variant sequences have been reported in Japan. However, we have noted five distinct, but related, genotypes (I-V) throughout the world, based on detailed sequence determination and analysis of the first 1700 nucleotides and part of the nonstructural region 5 at the C terminus of the open reading frame. The nucleotide sequence for a large number of hepatitis C virus isolates spanning six continents was obtained by direct sequence analysis of PCR products after reverse transcription. Genotype was classified by using several distinct sequence motifs. We observed that most genotypes coexist in several geographic regions, including the United States, Japan, Germany, and Italy. So far, genotype V has been found only in South Africa. Interestingly, each distinct genotype seems to be maintained throughout the genome in the segments studied. These genotype distinctions should be considered when designing specific diagnostic tests, developing potential vaccines, and studying viral transmission.

Amino Acid Sequence↗
PubMed1991

Characterization of the terminal regions of hepatitis C viral RNA: identification of conserved sequences in the 5' untranslated region and poly(A) tails at the 3' end.

We have determined the nucleotide sequence at the extreme 5' and 3' termini of the hepatitis C virus (HCV) genome. Our analyses of these sequences show (i) the nucleotide sequence in the 5' untranslated region is highly conserved among HCV isolates of widely varying geographical origin, (ii) within this region, there are blocks of nucleotide sequence homology with pestiviruses but not with other viruses, (iii) the relative position of short open reading frames present in the same region of the HCV genome is similar to that of the pestiviral genome, (iv) RNAs truncated at the 5' and 3' ends are found, but the origin and functions of these RNAs are unknown, and (v) poly(A) tails appear to be present on 3' subgenomic RNAs. These data differentiate HCV from the flaviviruses and indicate a closer evolutionary relationship of HCV with the pestiviruses. However, HCV also appears to be substantially different from other known pestiviruses. These data are consistent with the assignment of HCV to a separate viral genus.

Amino Acid Sequence↗
PubMed1991

Branched DNA amplification multimers for the sensitive, direct detection of human hepatitis viruses.

Branched oligonucleotides (bDNA) have been synthesized containing a unique primary segment and a set of identical secondary fragments covalently attached to the primary sequence through branch points. The primary sequence is designed to hybridize (directly or indirectly) to a target nucleic acid, such as hepatitis B virus (HBV) or hepatitis C virus (HCV) genomic DNA or RNA, respectively. The secondary fragments are used to direct the binding of multiple copies of a small oligonucleotide labelled with alkaline phosphatase. Assays for the presence of HBV and HCV based on the application of these branched amplification multimers have been devised. It is possible to detect as few as 1,000 hepatitis viral genomes directly.

Base Sequence↗
PubMed1979

Development of a method for the incorporation of substitution-inert metal ions into proteins. Site-specific modification of arsanilazotyrosine-248 carboxypeptidase A with cobalt(III).

This investigation demonstrates the use of substitution-inert metal ions as site-specific amino acid modifying reagents. The approach involves the production of a chelating agent at the site of interest with the subsequent in situ oxidation of substitution-labile cobalt(II) to exchange-inert cobalt(III) with H2O2. We have produced the chelate complex ethylenediamine-N,N'-diacetato(arsanilazotyrosinato-248 carboxypeptidase A)cobalt(III) [CoIII(EDDA)(AA-CPA-Zn)]. Model CoIII(EDDA)(azophenolate) complexes have helped to define the reaction conditions necessary to produce the enzyme derivative and have proved invaluable in the spectral analysis of the cobalt(III)-enzyme complex. The modified enzyme contains one active-site zinc and one externally bound cobalt per enzyme monometer. Circular dichroism and visible spectra of the derivative and apoenzyme substantiate the site-specific nature of the incorporation. Concimitant with CoIIIEDDA incorporation, the enzyme loses its peptidase activity yet maintains with FeIIEDTA returns the original properties of the arsanilazotyrosine-248 enzyme.

Amino Acids↗