An experiment is performed in which a point mutation is introduced randomly into the Zap-70 gene for a particular strain of mice.The mutant mice display a defect in T cell development.However,precursor T cells isolated from the thymus of these mice show normal expression levels of Zap-70 of the correct molecular weight.On further in vitro analysis,the mutant Zap-70 is found to bind to ITAM motifs in the cytoplasmic tail of the $\zeta$chain,but only when the $\zeta$chain is phosphorylated.No phosphorylated LAT is detected,however.Given these data,in which of the following protein domains is the mutation most likely to be present?
A)Pleckstrin homology (PH)domain
B)Proline-rich (PR)domain
C)SH1 domain
D)SH2 domain
E)SH3 domain

Question

Quizplus · Accepted Answer

In this experiment,the mutant Zap-70 can still bind to the phosphorylated $\zeta$ chains but cannot phosphorylate LAT.This suggests that the SH2 domains are normal but that the SH1 kinase domain has been mutated.Zap-70 does not contain a PH,PR,or SH3 domain.The PH domain allows proteins to localize to the membrane by binding to PIP3.PR domains mediate protein-protein interactions via binding to SH3 domains.

An Experiment Is Performed in Which a Point Mutation Is ζ\zetaζ

An Experiment Is Performed in Which a Point Mutation Is $\zeta$