•MOLECULAR CELL BIOLOGY • SIXTH EDITION • CHAPTER 3 • Protein Structure and Function

Lodish • Berk • Kaiser • Krieger • Scott • Bretscher •Ploegh • Matsudaira



• MOLECULAR CELL
BIOLOGY
• SIXTH EDITION
• CHAPTER 3
• Protein Structure and Function
© 2008 W. H. Freeman and Company

, Human
signaling
protein keapl




Ribbon diagram

,Conformations Functional classes:
Structural proteins Structural proteins
Scaffold protein Transport proteins
Transport protein Regulatory proteins
Regulatory protein
Motor proteins
enzymes



Different conformation = different function

, Hierarchical structure of proteins

Proteins are single, unbranched chains of amino acid monomers
There are 20 different amino acids; All amino acids have the same general
structure but the side chain (R group) of each is different
A protein’s amino acid sequence determines its three-dimensional structure
(conformation)
In turn, a protein’s structure determines the function of that protein




pK2 H pK1
+ -
H3N C COO

R