Question

1. Protein synthesis requires energy in the form of ATP and GTP. Two high-energy phosphate bonds (from ATP) fuel the formation of one aminoacyl tRNA. Formation of the initiation complex requires energy from one GTP. Delivery of each new tRNA to the Asite requires one GTP. Termination requires the hydrolysis of one GTP.   Based on this information, the table of codons, and your understanding of the processes of Activation, Initiation, Elongation, and Termination, answer the following questions.

a. How many high energy phosphate bonds are required for the translation of a 100 amino acid polypeptide, starting with mRNA, tRNA, amino acid and all the necessary enzymes

b. A portion of prokaryotic mRNA has the following base pair sequence: 5’ACAUCUA(U)GCCACGA3’. What would happen if the base in the brackets was mutated to an A.

Please solve both parts and explain in detail !! Thank you

Answer 1

Ans(a) As we can see in the given information, 2 phosphate bonds (from ATP) are used in the formation of one aminoacyl tRNA, two phosphate bonds (from GTP) are used in the formation of the initiation complex, two phosphate bonds (from GTP) are used in the delivery of each new tRNA to the Asite and two phosphate bonds (from GTP) are used in the termination.

Now, phosphate bonds for initiation and termination are used once and phosphate bonds for other reuirements are used for every amino acid.

Hence, for polypeptide of 100 amino acids:-

Phosphate bonds required for formation of initiation complex = 2 (It contains frst tRNA)

Phosphate bonds required for termonations = 2

phosphate bonds required for aminoacylation of tRNAs = 100 x 2 = 200

phosphate bonds required for delivery of new amino acid to asite = 99 x 2 = 198

Hence, total phosphate bonds required are = 2 + 2 + 200 + 198 = 402

Ans(b): The given mRNA sequence is-

5’ ACA UCU A(U)G CCA CGA 3’

Now, we know that codon AUG is start codon and initiator tRNA having its anticodon will bound to this codon and then, translation will start. If in the given mRNA sequence the base in bracket (U) was mutated to A then, initiator tRNA could not identify Start codon and cannot bind to mRNA chain. Hence, translation will not start.