For monosaccharides with two or more asymmetric carbons, the prefix d or l refers to the configuration of the highest numbered asymmetric carbon (the asymmetric carbon farthest from the carbonyl carbon).

TLS Online TPP Program

#Id: 7075

#Unit 3. Fundamental Processes

isoleucyl-tRNA synthetase has a nearby editing pocket (a deep cleft in the enzyme) that allows it to proofread the product of the adenylylation reaction. AMP-valine (as well as adenylylates of other small amino acids, such as alanine) can fit into this editing pocket, where it is hydrolyzed and released as free valine and AMP. In contrast, AMP-isoleucine is too large to enter the editing pocket and is therefore not subject to hydrolysis. As a consequence, isoleucyl-tRNA synthetase discriminates against valine twice: in the initial binding and adenylylation of the amino acid (discriminating by a factor of 100), and then in the editing of the adenylylated amino acid (again discriminating by a factor of 100), for an

overall selectivity of 10,000-fold (i.e., an error rate of 0.01%).

TLS Online TPP Program

#Id: 3201

#Unit 3. Fundamental Processes

Nucleotide excision repair (NER) systems excise a sequence that includes the damaged base(s). a new stretch of DNA is then synthesized to replace the excised material.

TLS Online TPP Program

#Id: 3226

#Unit 3. Fundamental Processes

Numerous proteins, including XP products and the transcription factor TFnH, are involved in eukaryotic nucleotide excision repair. 

TLS Online TPP Program

#Id: 1489

#Unit 4. Cell Communication and Cell Signaling

p53,  Induces the expression of CDK inhibitor p21 Induces apoptosis

TLS Online TPP Program

#Id: 10289

#Unit 4. Cell Communication and Cell Signaling

T-cell lineage