Consider the following two peptides, which may have been isolated from the floor of a Big Ten basketball arena circa 2000:

A: K-E-A-D-Y 

B: K-N-I-G-H-T

(a) Which peptide is more basic (has the higher isoelectric point)? Explain.

(b) Which peptide will emerge first from an anionexchange column at pH = 6.0?

(c) Which one of the following nucleotide sequences (3´-end on the left) could be the DNA sequence that codes for the biosynthesis of peptide A? Explain your reasoning.

Sequence 1: CGUGAAGCCGACUACUAA

Sequence 2: TTCCTTCGGCTGATA

Sequence 3: ATTATGGTGCGGGATGCA

Sequence 4: GCACUUCGGCUGAUGAUU

(d) Using abbreviated structures like those used in Fig. 27.4, give the structure of the aminoacyl-tRNA that codes for the first amino acid in the biosynthesis of peptide A. Include the sequence of residues in the anticodon region and the structure of the 3´ (acceptor) end.

Transcribed Image Text:

mRNA codon for amino acid 1 anticodon for amino acid 1 base OH ribosome C=O "P-site" R-CH NH, H₂N- (a) codon for amino acid 2 H anticodon for amino acid 2 base "R² OH ribosome "A-site" mRNA exit codon for amino acid 1 anticodon for amino acid 1 base OH OH ribosome "P-site" ribosome moves down the mRNA R 1 H |_c *NH, (b) codon for amino acid 2 anticodon for amino acid 2 base O 2 IR H OH ribosome "A-site" ribosome moves down the mRNA