Page 151 - Academic Press Encyclopedia of Physical Science and Technology 3rd BioChemistry

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Encyclopedia of Physical Science and Technology EN013D-616 July 27, 2001 12:5

Protein Structure

Ivan Rayment
University of Wisconsin, Madison

I. Introduction
II. Amino Acids
III. Protein Structure Determination
IV. Structural Hierachy
V. Secondary Structural Motifs
VI. Protein Stability
VII. Tertiary Structure
VIII. Membrane Proteins
IX. Superfamilies and Structural Evolution
X. Quaternary Structure
XI. Conclusions

GLOSSARY mer.Mostproteinsadoptawell-definedthree-dimensional
structure to fulfil their biological role. Thus, knowledge of
Primary structure Linear sequence of amino acids in a protein structure is central to understanding the molecular
polypeptide. basis of life.
Quaternary structure Arrangement of polypeptides in
macromolecular assembly.
Secondary structure A description of the three-dimen- I. INTRODUCTION
sional structure adopted by a localized sections of the
polypeptide chain. Proteins mediate the majority of biological processes. All
Tertiary structure A description of the arrangement of proteins share the common feature that they are condensa-
secondary structural elements within the protein. tion polymers of amino acids whose sequence is specified
˚
Units of length 1 A = 0.1 nm. by the genetic information contained within the genome
of the organism. Complete DNA sequences for organisms
ranging from Escherichia coli to humans suggest that the
PROTEINS are linear polymers of amino acids linked total number of proteins necessary for life lies in the range
by amide bonds where the biological function is dictated of 4200–50,000, although the number of genes in higher
by the sequence of amino acid residues within the poly- organisms is still under debate. Most of these proteins

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