Biomedical subjects

F Rixon

Publications and source records attributed to F Rixon.

5 recordsLinked to original sources

PubMed2001

Finding and using local symmetry in identifying lower domain movements in hexon subunits of the herpes simplex virus type 1 B capsid.

A characteristic of virus assembly is the use of symmetry to construct a complex capsid from a limited number of different proteins. Many spherical viruses display not only icosahedral symmetry, but also local symmetries, which further increase the redundancy of their structural proteins. We have developed a computational procedure for evaluating the quality of these local symmetries that allows us to probe the extent of local structural variations among subunits. This type of analysis can also provide orientation parameters for carrying out non-icosahedral averaging of quasi-equivalent subunits during three-dimensional structural determination. We have used this procedure to analyze the three types of hexon (P, E and C) in the 8.5 A resolution map of the herpes simplex virus type 1 (HSV-1) B capsid, determined by electron cryomicroscopy. The comparison of the three hexons showed that they have good overall 6-fold symmetry and are almost identical throughout most of their lengths. The largest difference among the three lies near the inner surface in a region of about 34 A in thickness. In this region, the P hexon displays slightly lower 6-fold symmetry than the C and E hexons. More detailed analysis showed that parts of two of the P hexon subunits are displaced counterclockwise with respect to their expected 6-fold positions. The most highly displaced subunit interacts with a subunit from an adjacent P hexon (P'). Using the local 6-fold symmetry axis of the P hexon as a rotation axis, we examined the geometrical relationships among the local symmetry axes of the surrounding capsomeres. Deviations from exact symmetry are also found among these local symmetry axes. The relevance of these findings to the process of capsid assembly is considered.

Capsid↗

PubMed1990

Identification and characterization of the virion protein products of herpes simplex virus type 1 gene UL47.

We have identified two encoded proteins with an antiserum raised against a synthetic oligopeptide corresponding to amino acids 671 to 684 of the predicted protein product of gene UL47 of herpes simplex virus type 1 (HSV-1). They have apparent Mrs of 82,000 and 81,000 and are both major virion components located in the tegument. The 82/81K proteins were first detected in infected cells in minor amounts 6 h after infection at 37 degrees C but were later (from 10 h until 24 h after infection) present in large amounts. UL47 regulation was investigated using phosphonoacetic acid (PAA), an inhibitor of DNA synthesis: the amounts of the 82/81K protein synthesized were compared with those of 65KDBP, an early gene product, and 21K/22K, a true late gene product. The data showed that UL47 is regulated as a true late gene.

Amino Acid Sequence↗

PubMed1990

Purification and biochemical characterization of chicken anaemia agent.

Chicken anaemia agent (CAA) was purified using differential centrifugation and successive cycles of equilibrium density gradient centrifugation using sucrose and CsCl. The purification method was dependent on the use of an antigen-detecting ELISA based on a CAA-specific monoclonal antibody. Virus particles banded at a density of 1.33 to 1.34 g/ml in CsCl and measured 23.5 +/- 0.8 nm in diameter. Purified preparations contained one major polypeptide (Mr 50,000) and a single-stranded, circular DNA (2.3 kb). CAA shares some of the biochemical characteristics possessed by porcine circovirus and the virus associated with psittacine beak and feather disease.

Animals↗

PubMed1985

Rise per base pair in helices of double-stranded rotavirus RNA determined by electron microscopy.

Regular helices of double-stranded RNA occur in nature only as the genome of certain viruses. The structure of such double-stranded RNA helices has been little studied compared to that of DNA, but some X-ray crystallographic data (Arnott, 1970; Saenger, 1984) are available. The recent advent of sequence data of bovine rotavirus RNA (Dyall-Smith et al., 1983; Elleman et al., 1983; Ward et al., 1984) has enabled us to determine by direct measurement of electron micrographs the translation, or axial distance between base pairs in RNA duplexes. Using two different spreading conditions we obtained values of 2.79 +/- 0.10 and 2.80 +/- 0.11 A. These results are consistent with the 11-fold A RNA (Arnott, 1970; Rosenberg et al., 1976) proposed for the conformation of double-stranded RNA. We included both circular and linear molecules of phi X174 RF DNA in the same preparations, and the translations for these molecules were between 3.23 +/- 0.06 and 3.29 +/- 0.05 A. Thus, double-stranded RNA contained 1.16 to 1.17 times more nucleotides per unit length than DNA.

Animals↗

PubMed1984

Rotavirus RNA segments sized by electron microscopy.

The RNA segments of bovine rotavirus (UK Compton strain) were measured by electron microscopy in mixtures containing phi X174 double-stranded DNA as an internal reference molecule. The numbers of base pairs per segment were calculated and compared with data obtained by other procedures (comparative RNA gel electrophoresis; co-electrophoresis of cDNAs in denaturing gels; sequencing).

Animals↗