How Many Different Aminoacyl- TRNA Synthetases Can Be Found in a Given

Question

How many different aminoacyl- tRNA synthetases can be found in a given organism's cells?
A) At least 20, or more depending on the organism
B) 16
C) 61
D) 20
E) The number varies greatly depending on the organisms type.

Accepted Answer

Aminoacyl-tRNA synthetases are enzymes that charge tRNAs with their corresponding amino acids. Since there are 20 standard amino acids that are incorporated into proteins by ribosomes during translation, at least 20 different aminoacyl-tRNA synthetases are required. However, some organisms may have more than 20 due to the presence of selenocysteine and pyrrolysine, which are considered the 21st and 22nd amino acids in some organisms.