Search PubMed⌕ Search

Biomedical subjects

J C Boothroyd

Publications and source records attributed to J C Boothroyd.

102 records · Page 6Linked to original sources
PubMed1982

The nucleotide sequence of cDNA coding for the structural proteins of foot-and-mouth disease virus.

The complete nucleotide sequence of cDNA coding for the structural capsid polypeptides of foot-and-mouth disease virus (FMDV) (strain A(10)61) has been determined. Portions of the flanking sequence coding for the nonstructural proteins p20a and p52 are also provided. The three larger structural polypeptides VP1, VP2 and VP3 have unmodified Mrs of 23248, 24649 and 24213, respectively. The size of the smaller polypeptide, VP4, can only be estimated at 7360 because the 5'-limit of its coding region is not yet known with certainty. The sequence data for VP1 (the major immunising antigen) and the amino-terminal quarter of p52 are compared with the data of Kurz et al. (Nucl. Acids Res. 9 (1981) 1919-1931) for a different serotype (O1K). This shows that variation is much greater in the region coding for VP1 than in that coding for p52. This is reflected in the level of amino acid sequence variation predicted for the two proteins. Analysis of relative codon usage reveals a strong bias in favour of C and G over U and A in the third base position. The dinucleotide frequencies show a bias against A-U and U-A, and for A-C and C-A.

Aphthovirus↗
PubMed1981

Homologous 3'-terminal regions of mRNAs for surface antigens of different antigenic variants of Trypanosoma brucei.

Sequences corresponding to the complete 3'-terminal regions of the messenger RNAs for three different Variant Surface Glycoproteins of Trypanosoma brucei were determined on complementary DNA inserts cloned in recombinant plasmids. The three sequences show 80-130 base pair long segments of strong (70-80%) homology at the 3' ends, whereas ther regions upstream from the last 130-140 base pairs contain no significant homology. The signal AAUAAA, present near the 3' ends of almost all known polyadenylated mRNAs of eukaryotes, does not occur in the 3'-terminal sequences of these three variants.

Amino Acid Sequence↗
PubMed1981

Molecular cloning of foot and mouth disease virus genome and nucleotide sequences in the structural protein genes.

Foot and mouth disease virus (FMDV), of the family Picornaviridae, consists of a single-stranded RNA (approximately 8,000 nucleotides), the translation of which is initiated on the 3' side of a 150-nucleotide poly(C) tract and yields a single polyprotein which is processed by host cell proteases into four primary products (Fig. 1). One or more virus-specified proteases further cleave these into the final products, the capsid proteins (VP1-4) being derived from the precursor p88 (for review see ref. 5). There are seven serotypes of the virus and as it has been shown that the immunizing activity of FMDV particles is associated primarily with VP1 (refs 6, 7), it seems likely that antigenic variation in FMDV is a result of changes in the structure of this protein. To further our understanding of this variation and as a first step in the possible development of FMDV vaccines from genetically manipulated microorganisms, we report here the construction and analysis of recombinant plasmids containing cDNA copies of the RNA. Comparison of the deduced amino acid sequence with the known polypeptide sequences shows that the NH2-termini of VP2 and VP3 are conserved between the A and O serotypes whereas that of VP1 (the immunizing antigen) varies by as much as 42% between serotypes.

Amino Acid Sequence↗
PubMed1981

Activation of trypanosome surface glycoprotein genes involves a duplication-transposition leading to an altered 3' end.

Expression of the genes for variant surface glycoproteins 117 and 118 in Trypanosoma brucei is accompanied by the appearance of an extra copy of these genes, the expression-linked copy, which differs in the surrounding restriction enzyme sites from the corresponding basic copy of the genes. We present direct evidence that the expression-linked copy is the one used for messenger RNA synthesis. By S1-nuclease-protection experiments we show that cloned basic-copy genes contain the nucleotide sequence of the corresponding messenger RNA except for the last 100 to 150 nucleotides before the poly(A) tail. Comparison of the 3'-terminal sequence of the 117 basic-copy gene and the 117 complementary DNA shows that this region differs by multiple point mutations, insertions and deletions, the differences starting within the coding sequence. Genomic blots demonstrate that a Bsp I site in the 3'-terminal part of the 118 complementary DNA is present in the expression-linked copy but not in the basic-copy gene. We conclude that expression-linked copies are the active genes, and that the generation of expression-linked copies involves a duplication--transposition in which the 3' end of the gene is replaced.

Amino Acid Sequence↗
PubMed1980

A variant surface glycoprotein of Trypanosoma brucei synthesized with a C-terminal hydrophobic 'tail' absent from purified glycoprotein.

Sequential expression of variant surface glycoproteins (VSGs) enables the parasitic protozoan Trypanosoma brucei to evade the immune response of its mammalian hosts. Studies of several VSGs, which have been isolated as soluble molecules following disruption of cells in the absence of detergent, have indicated extensive amino acid diversity and the absence of a hydrophobic segment which might serve to anchor the carboxy terminus to the membrane. The carboxy-terminal tryptic peptides of six VSGs have recently been characterized and shown to be glycosylated. Three of these VSGs terminated with a glycosylated aspartate or asparagine residue (Asx), suggesting that the VSG was cleaved following synthesis and glycosylation and before characterization. We present here nucleotide sequence data which suggest that the primary translation product of one VSG gene contains a hydrophobic tail at the carboxy terminus which is not found on the isolated, mature glycoprotein. The data also predict that the glycosylated residue is aspartic acid rather than the anticipated asparagine.

Amino Acid Sequence↗
PubMed1980

An introduction to antigenic variation in trypanosomes.

The salivarian trypanosomes have a unique capacity for antigenic variation at the cell surface. This phenomenon is their primary mechanism for evasion of the host's immune response. Variation is mediated through alternate expression of an extensive repertoire of variant surface glycoproteins (VSGs). Extensive amino acid sequence diversity is responsible for the antigenic diversity of VSGs. All the isolated VSGs of Trypanosoma brucei studied also contain an immunologically cross-reacting glycosyl side chain at the C-terminus, which probably represents a recognition site for proteolytic processing of the hydrophobic putative membrane-binding tail present on the synthesized molecule but not so far found on purified VSGs.

Amino Acid Sequence↗
PubMed1979

New genes and promoters suggested by the DNA sequence near the end of the coliphage T7 early operon.

We have employed the dideoxynucleotide chain-terminating method to determine the nucleotide sequence of T7 DNA between the physical map positions 18.9% and 19.8%. The most striking features of this sequence are two perfect 21-basepair repeats, each of which appears to contain a promoter for late transcription. In each case the promoter sequence incorporates a putative translational terminator on its left (5'-side of the "sense" strand), and overlaps a potential ribosome-binding site on its right. The region probably lies immediately distal to the early operon, and may contain two short, hitherto unreported protein-coding sequences.

Base Sequence↗
PubMed1976

Synchronous Growth and Plastid Replication in the Naturally Wall-less Alga Olisthodiscus luteus.

Olisthodiscus luteus is a unicellular biflagellate alga which contains many small discoidal chloroplasts. This naturally wall-less organism can be axenically maintained on a defined nonprecipitating artificial seawater medium. Sufficient light, the presence of bicarbonate, minimum mechanical turbulence, and the addition of vitamin B(12) to the culture medium are important factors in the maintenance of a good growth response. Cells can be induced to divide synchronously when subject to a 12-hour light/12-hour dark cycle. The chronology of cell division, DNA synthesis, and plastid replication has been studied during this synchronous growth cycle. Cell division begins at hour 4 in the dark and terminates at hour 3 in the light, whereas DNA synthesis initiates 3 hours prior to cell division and terminates at hour 10 in the dark. Synchronous replication of the cell's numerous chloroplasts begins at hour 10 in the light and terminates almost 8 hours before cell division is completed. The average number of chloroplasts found in an exponentially growing synchronous culture is rather stringently maintained at 20 to 21 plastids per cell, although a large variability in plastid complement (4-50) is observed within individual cells of the population. A change in the physiological condition of an Olisthodiscus cell may cause an alteration of this chloroplast complement. For example, during the linear growth period, chloroplast number is reduced to 14 plastids per cell. In addition, when Olisthodiscus cells are grown in medium lacking vitamin B(12), plastid replication continues in the absence of cell division thereby increasing the cell's plastid complement significantly.

Journal Article↗