During the night, COP1 enters the nucleus with the help of the COP9 signalosome complex (CSN).

TLS Online TPP Program

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#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

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#Unit 3. Fundamental Processes

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

TLS Online TPP Program

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#Unit 3. Fundamental Processes

Many Classes I aaRSs must recognize the anticodon to aminoacylate their cognate tRNAs.

TLS Online TPP Program

#Id: 3645

#Unit 3. Fundamental Processes

Several Class II enzymes do not interact with their bound tRNA’s anticodon.

TLS Online TPP Program

#Id: 3646

#Unit 3. Fundamental Processes

All Class I enzymes aminoacylate their bound tRNA’s 3′-terminal 2′-OH group, whereas Class II enzymes charge the 3′-OH group.