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 chain, but only when the 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 (P
H) domain
B)Proline-rich (P
R) domain
C)SH1 domain
D)SH2 domain
E)SH3 domain

Question

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  chain, but only when the  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 (P
H) domain 
B)Proline-rich (P
R) domain 
C)SH1 domain 
D)SH2 domain 
E)SH3 domain

Quizplus · Accepted Answer

In this experiment, the mutant Zap-70 can still bind to the phosphorylated 11ea40f0_b57b_0bbf_b42e_f3de16482ed4_TB1033_11 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