You want to test the role of a particular Cys residue in an enzyme by mutating i

Question

You want to test the role of a particular Cys residue in an enzyme by mutating it to another amino acid and seeing its effect on function. For the mutation, you want to pick an amino acid that is most similar in size and shape. Which amino acid would you pick and why? Give the full name, the 3 letter code, AND the 1 letter code. What types of amino acids would you most expect to see on the inside of a folded globular protein? Explain. Consider a reaction that occurs in human cells with a Delta G = 5 kJ mol^-1. What mechanisms could make reaction spontaneous? Explain.

Explanation / Answer

Cys is very similar to the amino acid Serine. in Cys sulfa hydroxy group (SH) is present and in Serine hydroxy group (OH) is present in the side chain. one and three letter code for this amino acid are - S and Ser.

in folded globular proteins we expect mostly hydrophobic amino acids and some of the polar or charged amino acids which make active site of enzymes.

if the delta G is negative then the reaction will be spontaneous. now, in this case, del G is positive. so to make this reaction spontaneous we must couple this reaction with ATP hydrolysis reaction. since ATP hydrolysis del G value is around -21 kJmol-1 . rest remaining energy will drive this reaction.

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