Your Friend Is Intrigued by Cdks and Purifies Cdk from the Daisy

question 60

Essay

Your friend is intrigued by Cdks and purifies Cdk from the daisy plant.She is able to determine the sequence of 18 amino acids from the daisy Cdk protein.Using these data, she aligns the daisy Cdk sequence with one human Cdk protein and the Cdk proteins from two different kinds of yeast, as shown in Figure 18-25.Sequences identical between the human and fungal proteins have been boxed.
Figure 18-25
Such conserved amino acid sequences are often involved in protein-protein interactions.Indeed, the threonine (T) in the central "YTHE" block is known to be phosphorylated by a kinase that activates Cdks in human and yeast.The surrounding conserved sequences could thus be important for the interaction of this Cdk-activating kinase with Cdk.In the daisy Cdk, however, not all of the amino acids in these conserved blocks match the sequences from yeast and human, as indicated by the arrows marked #1 and #2.
A.When you replace the S.cerevisiae (budding yeast) Cdk with the daisy Cdk, you discover the daisy Cdk does not interact with the Cdk-activating kinase inside the yeast cell.Circle the amino acid in the daisy Cdk that is likely to be the most disruptive to its interaction with Cdk-activating kinase.Explain.
B.Based on the information in Figure 18-25 and what you know about the Cdk1-Cdk-activating kinase interaction, would you predict that the human Cdk will interact with yeast Cdk-activating kinase? Explain.

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Definitions:

Guthrie

A psychologist recognized for his "contiguity theory" of learning, positing that associations between stimuli and responses are established through pairing or association.

Competing Associations

In learning and memory, the concept where multiple stimuli or ideas are linked to a single response or memory, leading to potential conflicts in recall or behavior.

Stimuli

External or internal elements that elicit responses from an organism or system.

S-R Association

The connection between a stimulus and the response it triggers, fundamental to behaviorist theories of learning and conditioning.