Download Uncommon amino acids, amino acids forming proteins

U NCOMMON AMINO ACIDS , AMINO ACIDS
FORMING PROTEINS , & PRIMARY STRUCTURE
OF A PROTEIN
UNCOMMON
A MINO A CIDS

Derived from common amino acids

Produced by the parent amino acid being
modified after protein is synthesized

Process is called post-translational modification
H YDROXYPROLINE &
HYDROXYLYSINE

Both examples of uncommon amino acids

Unlike their parent amino acids, both have
hydroxyl groups on their side chains

Found in some proteins in connective tissues

EX: Found in collagen
A MINO ACIDS FORMING
PROTEINS

This reaction takes place in the cells by a mechanism


Producing an amide.
Any 2 amino acids can be linked together to form dipeptides

The two amino acids are joined together by a peptide bond


Adding another would make it a tripeptide.
Every dipeptide still has a –COO and a –NH3

Amino acids can be linked in different ways to form different
dipeptides.

Some protein molecules contain more than 10,000 amino
acid units
F ORMING P ROTEINS

Shorter chains are referred to as peptides while
longer chains are referred to as polypeptides

Polypeptides contains a minimum of 30-50
amino acids

Residues are a chain of amino acids

Abbreviations of 1-3 letters are usually used to
represent proteins and peptides
S YNTHESIZING

C-terminus- amino acid at the end of a peptide
that has a free α-carboxyl group

N-terminus- amino acid at the end of a peptide
that has a free α-amino group

Proteins synthesize from the N-terminus to the
C-terminus
P ROTEINS P ROPERTIES

Continuing patterns of peptide bonds form the
backbone of peptides and proteins

Side chains- are called an R group

Up to 20 different side chains of the amino acid
supply variety and also determine the chemical
and physical properties of the protein


The most important property is acid-base
behavior
Amino acids behave like zwitterions as do
proteins
M ORE P ROPERTIES

In proteins repulsive forces between like charges
on their surfaces determine water solubility

When a protein is at a pH where there is an equal
number of positive and negative charges it is at
its isoelectric point

When proteins are at their isoelectric point they
are least soluble in water and can be precipitated
from the solution
P RIMARY S TRUCTURE

In a primary structure of a protein the sequence
of amino acids form a chain

Most peptides and protein molecules have
different sequences of amino acids


Each sequence allows the protein to perform its
function
Only a small fraction of all possible protein
molecules have been made by biological
organisms
P RIMARY S TRUCTURE

Like the naming of peptides the assignment of positions
of the amino acids starts at the N-terminal end

There are 20 possibilities for the N-terminal amino acid


400 different dipeptides can be formed from 20 amino
acids
The primary structure of a protein to a large extent,
determines the native, or most frequently reoccurring
secondary and tertiary structures
S EQUENCING

A change in sequence may or may not affect the
function of a protein depending upon the change


An example of this is how bovine insulin is used for
instant injections for humans. Even though the insulin is
not identical in structure to human insulin it still
performs the same task when introduced into a human.
Although it does perform the same task it is not as
effective.
An example of where a small change can have a huge
effect is in the protein of the blood, hemoglobin. A
change in one amino acid can cause the disease sickle
cell anemia