Question

Cathy is a young mum who is juggling a family of 2 young children, a part-time job and studying university part-time, so life is frequently stressful. However, recently she has been having some seizures. After several visits to specialists, her symptoms are an increased firing frequency in the neurons in some areas of her brain at diagnosed as being due to epilepsy, with Genetic tests she has just got back show that Cathy has a mutation from alanine to location in the voltage-gated sodium channels in her neurons. The mutation causes the channels to open at a lower membrane potential than normal. Part of the sequence in the mutated channel is glutamate-alanine-lysine, whereas it is normally alanine-alanine-lysine. glutamate at a key Note: The side chain structures of these amino acids are as follows: Alanine (Ala)-CH3 Glutamate (Glu)-CH2CH2COOH with a pKa of 4 Lysine (Lys) -CH2-CH2-CH2-CH2-NH3 with a pKa of 10 Answer the following questions based on this information Draw the structure of the tripeptide, glutamate-alanine-lysine, that this section of polypeptide is found in the middle portion of the protein's primary sequence (i.e. it is NOT at either the amino or carboxy terminal ends) as it would exist at pH 7. Note a) [8 marks]

Answer 1

CH3 Alanime PH ) COO H NH Glustamate COO C CHCHCOO H 1 생ine C CH-CH-CHCH-N 7/9

condlensation reaction amoved m NH Н, ий о we be be COO xemoved 8/9

Peptide bandl pH I- CONH C-CONH CONH C - HNO CH3 aine alanin Glutamat 9/9

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