tRNA and tRNA synthetases

How is the genetic code implemented?

![[Pasted image 20260303105748.png]] Wobble: there is greater leniency on the 3rd anticodon place. 1st codon in Anticodon is Inosine (3rd in codon) Inosine is deaminated adenosine!

![[Pasted image 20260303110335.png]]

31 different tRNAs needed

tRNA synthetases assign the codons

Also called aaRS = aminoacyl tRNA synthetases 20 different enzymes to join amino acids to their adaptors

Amino acid -> adenylated amino acid by tRNA synthetase -> AMP by tRNA synthetase ^Uses ATP-> 2 Pi + heat by pyrophosphatase ^tRNA -> Aminoacyl tRNA ![[Pasted image 20260303111254.png]]

Formation of charged tRNA (I)

Adenine goes to 3' end of tRNA by Class I aminoacyle-tRNA synthetases Or goes to 2' end by Class II aminoacyle-tRNA synthetases transesterification moves it to 3' anyway

Sources of error in translation 1.aaRS uses wrong amino acid as substrate 2.aaRS selects wrong tRNA as substrate 2. Ribosome selects wrong aa-tRNA for codon Proofreading in tRNA synthetases ![[Pasted image 20260303112241.png]] ![[Pasted image 20260303112313.png]]

Some aaRS proofread the aminoacyl-adenylate, others proofread the aa-tRNA. Some done proofread at all.