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Structural information on proteins obtainable from small‐angle X‐ray scattering with heavy‐atom labeling. Application to solubilized bacteriorhodopsin
Author(s) -
Kataoka M.,
Nakasako M.,
Tokunaga F.
Publication year - 1988
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/s002188988800319x
Subject(s) - bacteriorhodopsin , trimer , small angle x ray scattering , chemistry , crystallography , scattering , atom (system on chip) , molecule , physics , optics , dimer , membrane , biochemistry , organic chemistry , computer science , embedded system
The heavy‐atom labeling method is applied to small‐angle X‐ray scattering (SAXS) based on contrast variation in order to derive information on the inner structure of proteins. The formulation of the contrast variation is extended to express explicitly the contribution of the bound heavy atoms to SAXS. The present method reveals two important features concerning bound heavy atoms, namely their number and their distribution. The application of this method to solubilized bacteriorhodopsin (bR) with iodination revealed the following characteristics of structure. The number of bound iodine atoms is 20, indicating that the solubilized bR is composed of a trimer of bR molecules. The mean square distance between the iodine position and the center of the trimer is about 1660 Å 2 , indicating that the most active tyrosine residues are located near the outer rim of a bR trimer. The distribution of iodine atoms is symmetric about the center.