Some mitochondrial DNAs possess several D loops, reflecting the use of multiple origins. The same mechanism is employed in chloroplast DNA, where (in complex plants) there are two D loops.

TLS Online TPP Program

#Id: 3638

#Unit 3. Fundamental Processes

There are two class of AATS.
1.Class I – that transfer amino acid at 2’ OH and then 3’ OH &
2. Class II – that directly transfer the amino acid to 3’ OH

TLS Online TPP Program

#Id: 3639

#Unit 3. Fundamental Processes

Class I AATS are generally monomer and rarely dimer.

TLS Online TPP Program

#Id: 3640

#Unit 3. Fundamental Processes

Class II AATS are generally dimer and rarely tetramer.

TLS Online TPP Program

#Id: 3641

#Unit 3. Fundamental Processes

Class I and Class II aminoacyl–tRNA synthetases differ in several ways: Structural motifs, Anticodon recognition, Site of aminoacylation, Amino acid specificity.

TLS Online TPP Program

#Id: 3642

#Unit 3. Fundamental Processes

The Class I enzymes share two homologous polypeptide segments that are components of a dinucleotide-binding fold (Rossmann fold, which is also present in many NAD+- and ATP-binding proteins.

TLS Online TPP Program

#Id: 3643

#Unit 3. Fundamental Processes

The Class II synthetases lack the foregoing sequences but have three other sequences in common.