Chapter 3 – Protein Structure and Function
Chapter 3 - Protein Structure and Function
3.1 Hierarchical Structure of Proteins
3.2 Protein Folding
3.3 Protein Binding and Enzyme Catalysis
3.4 Regulating Protein Function
3.5 Purifying, Detecting, and Characterizing Proteins
3.6 Proteomics
Protein Structure and Function
3.1 Hierarchical Structure of Proteins
• Protein sequence specifies folding into secondary and
tertiary structures that either are functional units or
can interact with other peptides to form quaternary
structure functional units.
• Exceptional conformational flexibilities of disordered
proteins contribute to their multiple functions.
• Some polypeptides with dissimilar sequences fold into
similar 3D structures.
• Homologous proteins evolved from a common
ancestor, have similar sequences, structures, and
functions, and can be classified into families and
superfamilies.
Protein Structure and Function
• 3.2 Protein Folding
• Protein amino acid sequence determines its 3D
structure and function.
• ATP-dependent molecular chaperones and
chaperonins assist protein folding in vivo.
• Misfolded/denatured proteins can form wellorganized
amyloid fibril aggregates that can cause
diseases, including Alzheimer’s disease and
Parkinson’s disease.
Protein Structure and Function
3.3 Protein Binding and Enzyme Catalysis
• Protein function depends on binding other molecules
(ligands).
• Enzymes accelerate rates of cellular reactions by
lowering activation energy and stabilizing transitionstate
intermediates.
• Enzymes often use acid-base catalysis mediated by
one or more amino acid side chains.
• Metabolic pathway enzymes may be associated as
domains of a monomeric protein, subunits of a
multimeric protein, or components of a protein
complex assembled on a common scaffold.
Protein Structure and Function
3.5 Purifying, Detecting, and Characterizing Proteins
• Proteins can be isolated from other cell components
on the basis of a variety of physical and chemical
properties.
• Proteins can be detected and quantified by various
assays and specific antibody recognition.
• Tagging with various types of markers can be used to
investigate protein synthesis, location, processing,
and stability.
• X-ray crystallography, cryoelectron microscopy, and
NMR spectroscopy reveal 3D structures of proteins.