Download Chapter 3 Protein Structure and Function - UCO

Protein Structure and Function
Presented By Tyson
Sjulin
September 25, 2003
Primary Structure

Primary Structure is the linear arrangement, or sequence, of
the amino acid residues of the protein.
Secondary Structure


Secondary Structure is the various spatial arrangements
resulting from the folding of localized parts of the polypeptide
chain.
This is an example of β Sheet, which is stabilized by Hydrogen
Bonding.
Tertiary Structure


The tertiary structure of a protein is the three-dimensional
arrangement of all the amino acid residues.
This structure is stabilized by hydrophobic interactions and
hydrogen bonding between polar side chains.
Quaternary Structure

Quaternary Structure describes the number and relative
positions of the subunits in multimeric proteins, which are
proteins that consist of two or more polypeptides or subunits.
Chaperones Job in Determining Native
Conformation of Proteins


Chaperones bind and stabilize unfolded or partly folded
proteins, which prevents these proteins from being folded
incorrectly.
This is an example of heat-shock chaperonin-10 of
mycobacterium leprae.
Chaperonins Job in Determining
Native Conformation of Proteins


Chaperonins are large cylindrical macromolecular that partly
folder or misfolded polypeptides enter and then they are folded
into their native conformations.
The step which folds the polypeptide into its native
conformation is ATP-dependent.
Enzymes




All enzymes are proteins except for RNA-ribozymes.
High turnover number: rate of reaction is often enhanced 106 to
1012 times.
Active site is where catalysis occurs.
Enzymes exhibit specifity.
Chemical Modifications that many
Amino Acids Undergo


Nearly every protein in a cell is chemically modified
after its synthesis on a ribosome.
Types of Modification
– Acetylation- the addition of acetyl group (CH3CO)
to the Amino group of N-terminal residue.
– Phosphorylation- an phosphate group added to
serine, threonine, tyrosine, and histidine residues.
– Methylation- adding a methyl group to histidine
residues.
Kinetics of an enzymatic reaction are
described by Vmax and Km
Figure 3-26b
Conformational Change Induced by
Substrate Binding

When oxygen binds to one of the iron ions in an Hemoglobin, which
causes a conformational change in the hemoglobin.
Bioc 462a Lecture Notes
3.3 Allosteric transition between active
and inactive states
Figure 3-28
How Different Conditions Can
Determine Enzyme Activity

Each Enzyme has an optimal pH and
Temperature.
Effect of Enzyme on Activation Energy
References



Enzymes- The Biological catalysts. Timothy
Paustian. University of WisconsinMadison 17 Mar. 2003
http://www.enzymescatalysts.edu.
Protein Structure. Timothy Paustian. University of
WisconsinMadison 17 Mar. 2003
http://www.enzymescatalysts.edu.
Lodish, Harvey. Molecular Cell Biology. New York,
2003. Chapter 3.
http://www.whfreeman.com/lodish5e/>