Noonan syndrome type I with PTPN11 3 bp deletion: structure-function implications

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Noonan syndrome is linked to PTPN11 gene mutations in 40% of cases.
• PTPN11 encodes SHP-2, a protein tyrosine phosphatase regulated by its SH2 domains.
• Inhibition occurs via the N-terminal SH2 domain's D'EF loop insertion into the active site.

Purpose of the Study:

• To investigate the functional impact of a novel in-frame trinucleotide deletion (D61del) in the PTPN11 gene.
• To analyze the structural and energetic consequences of D61del on SHP-2 phosphatase activity.
• To compare the D61del mutant with a known gain-of-function mutant (D61Y).

Main Methods:

• Energetic-based structural analysis of wild-type and mutant SHP-2 proteins.
• Electrostatic calculations to predict protein stability and active site accessibility.
• Computational simulations of D61del and D61Y mutants compared to wild-type.

Main Results:

• The D61del mutation results in the removal of Aspartate 61 from the SHP-2 D'EF loop.
• D61del predicts decreased D'EF loop stability, enhancing active site access and phosphatase activity.
• Simulations indicate D61del and D61Y mutants exhibit increased catalytic cycles compared to wild-type SHP-2.

Conclusions:

• Aspartate 61 is crucial for the proper down-regulation of SHP-2 protein tyrosine phosphatase activity.
• The D61del mutation likely leads to an activated SHP-2 enzyme, potentially contributing to Noonan syndrome.
• Structural and computational analyses provide insights into SHP-2 regulation mechanisms.