Quaternary structure prediction, protein folding

Primary structure is determined, as we ve seen, by sequencing the pTotein. Secondary, tertiary, and quaternary structures are determined by X-ray crystallography (Chapter 22 Focus On) because it s not yet possible to predict computationally how a given protein sequence will fold. 

Visualizing Folded Protein Structures Primary Structure Determines Tertiary Structure Secondary Valence Forces Are the Glue That Holds Polypeptide Chains Together Domains Are Functional Units of Tertiary Structure Predicting Protein Tertiary Structure Quaternary Structure Involves the Interaction of Two or More Proteins... 

The crystal structure of CJueF from B. suhtilis was solved to 2.25 A, the protein exhibited a quaternary structure consisting of a dimer of hexamers (a dodecamer) belonging to the tunnel-fold superfamily, where substrate binding is believed to be at the subunit interface. To confirm the role of the enzyme in vitro, the genes from B. suhtilis and E. coli were cloned and expressed. After determining that the predicted GTP cyclohydrolase activity was not exhibited by CJiieF from these two species, alternative roles were explored. 

Over the last decade, using reduced protein models, considerable progress has been made towards understanding the nature of the protein folding process as well as in the development of techniques to predict low resolution tertiary and in some ca.ses quaternary structure from protein sequence. Becau.se they reduce the number of degrees of freedom, reduced or simplified protein models can address aspects of... 

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