What amino acid is made to replace another amino acid in membrane-spanning $\alpha$-helices by site-directed mutagenesis of the gene coding for the protein? This is done in order to determine how close together two such $\alpha$-helices are in the structure of an integral protein.The amino acid is added to facilitate the formation of crosslinks between $\alpha$-helices that are in close proximity.
A)phenylalanine
B)alanine
C)cysteine
D)methionine
E)proline

Question

Quizplus · Accepted Answer

Cysteine has a thiol group (-SH) that can form disulfide bonds with another cysteine molecule. This property can be used for crosslinking the F1F1F1S1F1F1F10-helices that are in close proximity. Therefore, cysteine is the best choice for replacing another amino acid to facilitate crosslinking and determine the proximity of the helices.

What Amino Acid Is Made to Replace Another Amino Acid α\alphaα

What Amino Acid Is Made to Replace Another Amino Acid $\alpha$