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The three‐dimensional structure of a human IgGl immunoglobulin at 4 Å resolution: a computer fit of various structural domains on the electron density map
Author(s) -
Sarma R.,
Laudin A. G.
Publication year - 1982
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s002188988201245x
Subject(s) - fragment (logic) , molecule , chemistry , crystallography , electron density , resolution (logic) , crystal structure , molecular replacement , immunoglobulin fab fragments , electron , physics , peptide sequence , mathematics , algorithm , biochemistry , organic chemistry , quantum mechanics , artificial intelligence , computer science , gene , complementarity determining region
The crystal structure of an intact IgG1 immunoglobulin molecule (DOB) has been determined at a resolution of 4 Å from an electron density map calculated with phases for the reflections derived using the multiple isomorphous replacement method. The map has been interpreted by rotation and translation of known structures of the various fragments of the IgG molecule. The Fc fragment, the constant domains (CH1 and CL) of the Fab fragment and the variable domains (VH and VL) of the Fab fragment were rotated and translated in the DOB unit cell and superposed on the calculated electron density map. The total number of rotational and translational parameters for each fragment was determined using several known and expected features of the IgG molecule. The superposition was quantitated by accumulating the electron density values at the various α‐carbon atoms. The three fragments investigated gave in each case one peak thus unambiguously providing the parameters relating each fragment with the DOB molecule. The final structure shows two possible ways of joining the CH1 domain of the Fab fragment with the CH2 domain of the Fc fragment. A refinement of the model is expected to resolve this ambiguity.