BIO130H1 Lecture Notes - Lecture 4: Opioid Peptide, Alpha Helix, Beta Sheet

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3 Feb 2016
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21/01/16
BIO 130 – Lecture 4 – Amino acid and Protein Structure
Structure of the Genetic Code:
Groups of nonpolar, polar (charged and uncharged), and others can be found in codon
table (in textbook)
Genetic code is universal
Genetic code is degenerate – there is a high degree of redundancy (ex: more than one
mRNA codon can code for a Proline)
oDon’t mix up with ambiguity
Similar amino acids (AA) are close to each other on the table
Mutational Steps between Codons:
What is the minimum number of mutational steps between amino acids?
o# mutations between codons for different AA’s
How many mutational steps required to get from a codon for proline to one for cysteine,
minimum?
o2
How many mutational steps required to get from a codon for proline to one for cysteine,
maximum?
o3
Review:
Groups of AA’s with similar properties tend to be clustered in the codon table
Codons of AA’s with similar properties tend to have fewer mutational steps between
them
One random mutation in a codon is less likely to result in a dramatic change in amino
acid properties than two random mutations
Synthesis of Proteins:
Carboxyl group on one AA reacts with amino group of other AA and forms peptide bond
Peptide bond is covalent, rigid and planar
Condensation takes place when protein is being formed and creates water
Protein has an amino end and carboxy end
The order of AA’s is important
oThis is Leu-Enkephalin – a pentapeptide of Tyr-Gly-Gly-Phe-Leu
oIt is a natural opioid peptide which down modulates the perception of pain
oThe pentapeptide Leu-Phe-Gly-Gly-Tyr (inverse) has no pharmacological effects
oThe NH2-COOH orientation of the peptide is essential for function
The Alpha Helix:
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