Domains and Tertiary Structures of Proteins

Complementary packing surfaces are the key link to the next hierarchical level, tertiary stmcture. Tertiary interactions arise because distant parts of a protein interact across what might be called an intramolecular interface. There is a consensus that tertiary stmcture entails at least two new concepts  

The main chain adopts a characteristic fold with some degree of imprecision, both with respect to primary stmcture encoding (Jones et al, 1992 Srinivasan and Rose, 1995) and to the mechanism of renaturation (Dill and Chan, 1997). 

Packing or stereochemical complementarity (Richards and Lim, 1993) is an important source of the new bonding interactions, required to stabilize unique native stmcture. 

CxxCH Heme attachment Cyt c3, c551, c Cyt f This motif binds covalently to a heme group via two Cys and coordinates the bound iron with His of many homologous cytochromes. 

CxxxxxRS Phosphatase (type I/II) Type I and II Pases The motif is contained within a loop connecting a P-strand to an a-helix around the active site. 

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