An Experiment Is Performed in Which a Point Mutation Is

Multiple Choice

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 (PH) domain
B) Proline-rich (PR) domain
C) SH1 domain
D) SH2 domain
E) SH3 domain