INTRODUCTION

                                                Copyright: J. E. Wampler, 1996

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This tutorial covers the basics of peptide and protein structure and consists of four parts:

I. Primary Structure.

II. Secondary Structure.

III. Tertiary Structure.

IV. Quaternary Structure.

Continue with this page to see definitions of these four structural elements and generalizations about protein folding.

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Proteins and peptides are biopolymers composed of amino acid residues interlinked by amide bonds. Their structure can be discussed in terms of four levels of complexity defined as follows:

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WHAT DO WE KNOW ABOUT PROTEIN FOLDING?

• around 4000 known structures from X-ray crystallography and 2-D NMR studies

• structure data base widely available for analysis, the Protein Data Bank

• water soluable proteins are "globular," tight packed, water excluded from interior, folded up.

• bond lengths and bond angles don't vary much from equilibrium positions.

• structures are stable and relatively rigid.

• folding possibilities are limited, both along the backbone chain and within the side chain groups.

• folding motifs are used repetitively.

• proteins with similar function typically have similar structure.

• with similar proteins (say from different organisms) structure tends to be more conserved than the exact sequence of amino acids.

• although sequence must determine structure, it is not yet possible to predict the entire structure from sequence accurately.

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Continue tutorial.