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.

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:

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.

Continue tutorial.