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M S Chapman

Publications and source records attributed to M S Chapman.

At least 55 records · Page 3Linked to original sources
PubMed1994

Sequence similarity scores and the inference of structure-function relationships.

Improved methods are described for the interpretation of two or more aligned protein or nucleic acid sequences. These methods can be used to interpret the possible biological importance of regions within a known three-dimensional structure, or, even without a structure, to correlate sequence similarity with the known function of particular amino acids and to associate sequence similarity with properties predicted from the sequences. Improvements include the calculation of a position-dependent, gap-penalized similarity score; computer-assisted graphical association of sequence similarity with structural, functional or chemical properties of the sequences; and statistical comparisons of the sequence conservation or variability of different groups of residues. An application is described to analyze the sequences of piconarviral capsid proteins.

Algorithms↗
PubMed1993

A comparison of the anti-rhinoviral drug binding pocket in HRV14 and HRV1A.

The three-dimensional structures of two human rhinovirus serotypes (HRV14 and HRV1A) are compared when complexed with various antiviral agents. Although these agents all bind into the same hydrophobic pocket, the exact viral-drug interactions differ. In the absence of drugs, the pocket is occupied by a fatty acid in HRV1A, but is empty in HRV14 except for two water molecules. The conformation of each drug is dependent upon the shape of the hydrophobic pocket. In HRV14 the major residues determining the shape of the binding site are Y1128, P1174 and M1224, corresponding to I1125, M1169 and I1220 in HRV1A. When there is no cofactor or a drug in the pocket, the entrance to the pocket is open. However, the entrance is closed when the pocket is occupied by a cofactor or a drug. There are relatively small conformational changes when the agents displace the natural cofactor in HRV1A. In contrast, there are much larger conformational changes on binding a drug in HRV14. These differences cause an inhibition of viral attachment in HRV14 but not in HRV1A. Binding of the drugs results in three additional interprotomer hydrogen bonds in HRV14 and one in HRV1A. These hydrogen bonds and a potential loss of flexibility upon efficient packing of the pocket may contribute to the inhibition of uncoating in both serotypes.

Amino Acid Sequence↗
PubMed1993

Mapping the surface properties of macromolecules.

Methods are presented for the rapid computation of schematic projections of the surfaces of macromolecules, similar to the "roadmaps" used to illustrate the surfaces of viruses (Rossmann, M.G. & Palmenberg, A.C., 1988, Virology 164, 373-382). Several types of projections are described, extending the application of "roadmaps" to the external surfaces of all macromolecules and their interior binding pockets and pores. The surface projections, showing the positions of residues, can be colored, shaded, contoured, and annotated to show physical, sequence, or functional properties such as surface topology, hydrophobicity, or sequence conservation, for example. The automated procedures are useful for surveys of the surface features of proteins sharing similar functional properties.

Computer Graphics↗
PubMed1993

Structure, sequence, and function correlations among parvoviruses.

The capsid protein sequences of 10 representative parvoviruses were aligned against the sequence and three-dimensional structure of canine parvovirus (CPV). The structure of CPV was then analyzed after mapping onto it position-dependent sequence similarity scores and the locations of residues that are phenotypically important in other parvoviruses. Antigenicity is primarily associated with external exposed loops of high sequence variability. Amino acids in the canyon, a surface depression encircling each fivefold axis, are well conserved, but may have a function other than external receptor binding. Residues important to parvoviral cell specificity and erythrocyte binding are scattered near the rim of a less-conserved depression near the twofold axis, and on a shoulder of the threefold spike. The number of residues involved in various interactions and their conservation and properties suggest that uncoating may involve separation of fivefold and twofold related subunits before those related by threefold symmetry. The inner surface residues of the capsid are generally more highly conserved than those on the outer surface, presumably due to interactions with DNA, although the binding site that contains ordered DNA in the structure is not especially conserved.

Amino Acid Sequence↗
PubMed1993

Comparison of surface properties of picornaviruses: strategies for hiding the receptor site from immune surveillance.

The surface topology and sequence conservation of different picornaviruses have been compared using molecular graphics and statistical analyses. The comparisons suggest that the canyons, surface depressions encircling the fivefold axes, are the sites of receptor attachment of enteroviruses as well as human rhinovirus (HRV). In HRV14, the receptor binding footprint extends beyond the canyon (Olson et al. (1993), Proc. Natl. Acad. Sci. USA 90, 507-511), but these more exposed regions are not conserved in polioviruses or minor receptor group rhinoviruses, suggesting some differences in receptor binding. When rhinoviruses are compared to other picorna- and parvoviruses, the surface sequence similarity relative to the similarity of buried residues is about the same. Thus, the effect of host immune surveillance on surface residues is similar. Therefore, it is probable that some means of protecting a conserved binding site from immune detection (such as a canyon) will be an essential requirement in other viruses. However, there may be other strategies for achieving this result. For instance, as in foot-and-mouth disease virus, the receptor attachment site of Mengo virus is associated with a flexible structural component which may inhibit the production of neutralizing antibodies that are able to recognize only one explicit conformation.

Picornaviridae↗
PubMed1992

Conformationally restricted analogues of disoxaril: a comparison of the activity against human rhinovirus types 14 and 1A.

A series of conformationally restricted analogs of disoxaril has been synthesized and evaluated against human rhinovirus types (HRV) 14 and 1A. The sensitivity of these serotypes to this series varied and was dependent upon the length of the molecule as well as upon the flexibility of the aliphatic chain. Minimum energy conformations of these compounds were overlaid with the X-ray structure of a closely related analog 9 bound to the capsid protein of both HRV-14 and -1A and then modeled in the compound-binding site of both serotypes. A comparative sweep volume of these compounds about the isoxazole ring revealed an inaccessible region of space for the cis-olefin 8b, which is not the case for either the trans-olefin 8a or the acetylene 5. This region may be important to the binding of the compounds to the HRV-14 site particularly during entry into the pocket.

Antiviral Agents↗
PubMed1992

Ab initio phase determination for viruses with high symmetry: a feasibility study.

Conditions that would permit the complete structure determination of spherical viruses that have high internal symmetry were examined starting only from an initial spherical shell model. Problems were considered that might arise due to the following. 1. Creation of centric phases due to the simple shell model and its position in the unit cell. The centric symmetry can generally be broken on averaging an initial electron density map based on observed structure amplitudes, provided that the internal molecular symmetry is sufficiently non-parallel to the crystallographic symmetry. 2. Choice of the average model shell radius. Some incorrect radii led to the Babinet opposite solution (electron density is negative instead of positive). Phases derived from other models with incorrect radii failed to converge to the correct solution. 3. Error in structure amplitude measurements. 4. Lack of a complete data set. 5. Error in positioning the initial spherical-shell model within the crystal unit cell. It was found that an error of 1.6 A caused noticeable phasing error at a resolution greater than 20 A.

Feasibility Studies↗
PubMed1992

Ab initio phase determination for spherical viruses: parameter determination for spherical-shell models.

The structure determination of canine parvovirus depended on the extension of phases calculated initially from a spherical-shell model [Tsao, Chapman, Wu, Agbandje, Keller & Rossmann (1992). Acta Cryst. B48, 75-88]. Such ab initio phasing holds the promise of obviating initial experimental phasing by isomorphous or molecular replacement, thereby expediting the structure determinations of spherical virus capsids. In this paper, it is shown how parameters such as radii, DNA density and particle positions may be determined and refined from diffraction data with sufficient precision to start phase extension from 20 A resolution for a virus of approximately 122 A radius.

Capsid↗
PubMed1992

Structure determination of monoclinic canine parvovirus.

The three-dimensional structure of the single-stranded DNA canine parvovirus has been determined to 3.25 A resolution. Monoclinic crystals belonging to space group P2(1) (a = 263.1, b = 348.9, c = 267.2 A, beta = 90.82 degrees) were selected for data collection using primarily the Cornell High Energy Synchrotron Source and oscillation photography. There was one icosahedral particle per crystallographic asymmetric unit, giving 60-fold redundancy. The particle orientations in the unit cell were determined with a rotation function. The rough positions of the particles in the unit cell were estimated by considering the packing of spheres into the P2(1) crystal cell. More accurate particle centers were determined from Harker peaks in a Patterson function. Hollow-shell models were used to compute phases to 20 A resolution. The radii of the models were based on packing considerations, the fit of spherical shells to the low-resolution X-ray data and low-angle solution scattering data. The phases were extended to 9 A resolution using molecular replacement real-space averaging. These were then used to determine the heavy-atom position of a K2PtBr6 derivative, for which only 5% of the theoretically observable reflections had been recorded. The center of gravity of the 60 independent heavy-atom sites gave an improved particle center position. Single isomorphous replacement phases to 8 A resolution were then calculated with the platinum derivative. These were used to initiate phase improvement and extension to 3.25 A resolution using density averaging and Fourier back-transformation in steps of one reciprocal lattice point at a time. The resulting electron density map was readily interpretable and an atomic model was built into the electron density map on a PS390 graphics system using the FRODO program. The R factor prior to structure refinement for data between 5.0 and 3.25 A was 36%.

Crystallization↗
PubMed1991

The three-dimensional structure of canine parvovirus and its functional implications.

The three-dimensional atomic structure of a single-stranded DNA virus has been determined. Infectious virions of canine parvovirus contain 60 protein subunits that are predominantly VP-2. The central structural motif of VP-2 has the same topology (an eight-stranded antiparallel beta barrel) as has been found in many other icosahedral viruses but represents only about one-third of the capsid protein. There is a 22 angstrom (A) long protrusion on the threefold axes, a 15 A deep canyon circulating about each of the five cylindrical structures at the fivefold axes, and a 15 A deep depression at the twofold axes. By analogy with rhinoviruses, the canyon may be the site of receptor attachment. Residues related to the antigenic properties of the virus are found on the threefold protrusions. Some of the amino termini of VP-2 run to the exterior in full but not empty virions, which is consistent with the observation that some VP-2 polypeptides in full particles can be cleaved by trypsin. Eleven nucleotides are seen in each of 60 symmetry-related pockets on the interior surface of the capsid and together account for 13 percent of the genome.

Amino Acid Sequence↗
PubMed1991

Human rhinovirus 14 complexed with antiviral compound R 61837.

The binding of the antirhinoviral agent R 61837 to human rhinovirus 14 has been examined by X-ray crystallographic methods. The compound R 61837 binds in the same pocket (underneath the canyon floor) as the "WIN" antirhinoviral agents. It does not penetrate as far into the pocket but causes similar conformational changes in the virus capsid. The movement of residues 1217 to 1221 of viral protein 1 (in the "FMDV loop") is more pronounced for R 61837 than for WIN compounds. Although both R 61837 and WIN antiviral agents partially fill the same hydrophobic pocket, atomic binding interactions differ, showing that considerable diversity in the nature of antiviral agents is possible.

Antiviral Agents↗
PubMed1990

Modeling of the human intercellular adhesion molecule-1, the human rhinovirus major group receptor.

A model has been built of the amino-terminal domain of the intercellular adhesion molecule-1 (ICAM-1), the receptor for most human rhinovirus serotypes. The model was based on sequence and presumed structural homology to immunoglobulin constant domains. It fits well into the putative receptor attachment site, the canyon, on the human rhinovirus-14 (HRV14) surface in a manner consistent with most of the mutational data for ICAM-1 (Staunton, D. E., Dustin, M. L., Erickson, H. P., Springer, T. A. Cell, in press, 1989) and HRV14 (Colonno, R. J., Condra, J. H., Mizutani, S., Callahan, P. L., Davies, M. E., Murcko, M. A. Proc. Natl. Acad. Sci. U.S.A. 85: 5449-5453, 1988).

Amino Acid Sequence↗
PubMed1989

Crystal structure of human rhinovirus serotype 1A (HRV1A).

The structure of human rhinovirus 1A (HRV1A) has been determined to 3.2 A resolution using phase refinement and extension by symmetry averaging starting with phases at 5 A resolution calculated from the known human rhinovirus 14 (HRV14) structure. The polypeptide backbone structures of HRV1A and HRV14 are similar, but the exposed surfaces are rather different. Differential charge distribution of amino acid residues in the "canyon", the putative receptor binding site, provides a possible explanation for the difference in minor versus major receptor group specificities, represented by HRV1A and HRV14, respectively. The hydrophobic pocket in VP1, into which antiviral compounds bind, is in an "open" conformation similar to that observed in drug-bound HRV14. Drug binding in HRV1A does not induce extensive conformational changes, in contrast to the case of HRV14.

Amino Acid Sequence↗
PubMed1988

Tertiary structure of plant RuBisCO: domains and their contacts.

The three-dimensional structure of ribulose-1,5-biphosphate carboxylase-oxygenase (RuBisCO), has been determined at 2.6 A resolution. This enzyme initiates photosynthesis by combining carbon dioxide with ribulose bisphosphate to form two molecules of 3-phosphoglycerate. In plants, RuBisCO is built from eight large (L) and eight small (S) polypeptide chains, or subunits. Both S chains and the NH2-terminal domain (N) of L are antiparallel beta, "open-face-sandwich" domains with four-stranded beta sheets and flanking alpha helices. The main domain (B) of L is an alpha/beta barrel containing most of the catalytic residues. The active site is in a pocket at the opening of the barrel that is partly covered by the N domain of a neighboring L chain. The domain contacts of the molecule and its conserved residues are discussed in terms of this structure.

Amino Acid Sequence↗
PubMed1987

A crystal form of ribulose-1,5-bisphosphate carboxylase/oxygenase from Nicotiana tabacum in the activated state.

A new crystal form of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) from Nicotiana tabacum has been obtained at alkaline pH with polyethylene glycol 8000 in the presence of a non-ionic detergent, beta-octyl glucoside. The crystals are grown at room temperature by the hanging-drop vapor diffusion technique from a protein solution containing enzyme complexed with CO2, Mg2+, and the transition state analog 2-C-carboxy-D-arabinitol-1,5-bisphosphate. The crystals belong to the the space group P3(1)21 (or P3(2)21) with the cell parameters a = 204.6 A, and c = 117.4 A (1 A = 0.1 nm). The asymmetric unit contains half (L4S4: L, large subunit, 53,000 Mr; S, small subunit, 15,000 Mr) of a hexadecameric molecule (L8S8, 540,000 Mr). The crystals diffract to at least 2.6 A Bragg spacing and are suitable for X-ray structure determination.

Crystallization↗
PubMed1986

Structural studies of Rubisco from tobacco.

An electron density map of ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) from tobacco (Nicotiana tabacum) has been obtained by X-ray crystallography at a nominal resolution of 0.34 nm. Phases were determined by multiple isomorphous replacement with three heavy atom derivatives and then refined by solvent flattening. Rubisco is barrel-shaped, and has (422) symmetry. The fourfold axis runs down an open central channel, concentric with the barrel. The molecule measures 10.5 nm along the fourfold axis, and has a diameter of 13 nm perpendicular to the fourfold axis at the widest point. The diameter of the central channel is 2.8 nm at the centre of the molecule, and 0.6 nm at its narrowest constriction. Portions of the polypeptide backbone of the promoter have been traced and some 127 residues have been assigned to 14 alpha-helices. The amino acid sequences of Rubisco from Rhodospirillum rubrum and from the large subunit of tobacco are sufficiently similar to suggest that the two chains are folded in the same general way.

Models, Molecular↗
PubMed1978

Serological evidence of continuing infection of swine in Great Britain with an influenza A virus (H3N2).

Serum samples collected from swine and cattle in Great Britain at various times between July 1971 and July 1977 were examined by haemagglutination-inhibition or single radial haemolysis methods for evidence of infection with influenza A (H3N2) viruses. A small proportion of swine sera collected in each year reacted in the tests but there was no evidence of infection in cattle. The significance of the findings is discussed, with particular reference to the seasonal fluctuations in the prevalence of antibody in swine observed during the period of the study, and their possible relevance to influenzal events in the human population. None of the sera tested had antibody to swine influenza strains (HSw1N1).

Animals↗