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Biomedical subjects

P M Colman

Publications and source records attributed to P M Colman.

At least 73 records · Page 4Linked to original sources
PubMed1976

Crystallographic structure studies of an IgG molecule and an Fc fragment.

The crystal structures of a human IgG antibody molecule Kol and a human Fc fragment have been determined at 4-A and 3.4-A resolution respectively, by isomorphous replacement. The electron-density maps were interpreted in terms of immunoglobulin domains based on the Rei and McPC 603 models (Kol) and by model-building (Fc). The Fab parts of Kol have a different quaternary structure from that observed in isolated crystalline Fab fragments, there being no longitudinal V-C contact in Kol. The Fc part C terminal to the hinge is disordered in the Kol crystals. It is suggested that the Kol molecule is flexible in solution, whereas fragments are rigid. In the Fc fragment both CH3 and CH2 show the immunoglobulin fold. The CH3 dimer aggregates as CH1-CL while CH2 are widely separated from each other. The carbohydrate bound to Fc is in fixed position. From these structures a hypothetical liganded antibody molecule has been constructed, which is assumed to be rigid.

Antigen-Antibody Reactions↗
PubMed1976

Subunit symmetry of tetrameric phosphorylase a.

Native crystallographic data of tetrameric phosphorylase a crystals, space group P21, have been collected photographically to 3 A resolution. These data have been used in Patterson search methods in reciprocal and real space. The tetramers were found to exhibit molecular 222 symmetry. The cross vector between the centres of the two symmetry related tetramers in the unit cell was determined by two different translation function methods. On the basis of these rotation and translation function results a model for the arrangement of monomers within the tetramer and of tetramers in the unit cell is proposed; The 222 symmetry of the tetrameric molecule is found only when high resolution diffraction data are included (i.e. higher than 6 A). At lower resolution other symmetries dominate. Calculations with the proposed model have shown that these spurious symmetries result from the nonspecific overlap of protein-protein and solvent-solvent cross vectors. These results emphasize the importance of high resolution data when noncrystallographic symmetry of globular proteins is studied.

Chemical Phenomena↗
PubMed1976

Crystallographic structural studies of a human Fc-fragment. I. An electron-density map at 4 A resolution and a partial model.

The crystal structure of a human Fc fragment was analysed at 4 A resolution. A partial interpretation of the electron-density map in terms of domain structure was possible. The molecule has the shape of a mickey mouse. The spherical domain was interpreted visually and by domain Patterson function interpretation as the CH3 dimer. This dimer resembles closely the CH1-CL dimer found in Fab structures. The ellipsoidal "ears" of the molecule represent the CH2 domains. They are widely separated from each other, but closely connected to CH3. Their tertiary structure must be different from CH1, as Patterson domain interpretations were unsuccessful. A chain tracing in CH2 was not yet possible.

Crystallography↗
PubMed1976

Crystallographic structural studies of a human Fc fragment. II. A complete model based on a Fourier map at 3.5 A resolution.

The crystal structure analysis of a human Fc fragment was pursued to 3.5 A resolution and a complete model was built and refined into the isomorphous Fourier map. The CH2 and CH3 domains show the immunoglobulin fold, with CH3 being closely similar to CH1, but CH2 intermediate in structure between V and CH3. The carbohydrate is rigidly attached to CH2, covering the C face. CH3 dimerizes as CH1-CL, but CH2 has no contact to the second chain. Residues involved in the lateral CH3-CH3 and the longitudinal CH3-CH2 contact are conserved in Ig classes and sub-classes. In IgM and IgE the two C-terminal domains also show this characteristic distribution of contact residues.

Carbohydrates↗
PubMed1975

The structure determination of the variable portion of the Bence-Jones protein Au.

The structure of a pi-type Bence-Jones protein variable fragment Au has been determined by molecular replacement methods using the known structure of an other Bence-Jones variable fragment Rei (Epp et al., Eur J. Biochem. 45, 513 (1974). The crystallographic R factor is 0.31 for about 4000 significantly measured reflections between 6.8 to 2.5 A. The Au protein forms a dimer across a crystallographic two fold axis. The spatial relationship of the two monomers, the conformation of the backbones and of the internal residues is extremely similar to that found in Rei.

Amino Acids↗