Eine verbesserte Drehkorrelationsmethode für die Strukturbestimmung biologischer Makromoleküle durch Mittelung elektronenmikroskopischer Bilder

Abstract

The averaging of EM of biological macromolecules by correlation techniques can be performed if the molecules lie in the plane of the support film. To improve the normal method which uses the autocorrelation function to determine the orientation of the molecules, a new method and its computer realization was devised using iterative, translational and rotational correlations of the molecule images themselves. With this method the symmetry properties of yeast fatty acid synthetase were studied. The new method is very precise (angle accuracy .apprx. .+-. 1.degree.). Fatty acid synthetase contains a 3-fold rotation axis. A cyclic symmetry (C3) of the structure is likely. The .alpha.-subunit consists of at least 2 protein domains.