Structural Characterization of 5-Substituted Pyrrolo[3,2-d]pyrimidine Antifolate Inhibitors in Complex with Human...

Area of Science:

• Biochemistry
• Structural Biology
• Medicinal Chemistry

Background:

• Previously discovered pyrrolo[3,2-d]pyrimidine antifolates show potent antitumor activity by inhibiting serine hydroxymethyltransferase 2 (SHMT2).
• Understanding the structural basis of SHMT2 inhibition is crucial for optimizing these novel anticancer agents.

Purpose of the Study:

• To present crystallographic structures of SHMT2 in complex with an expanded series of pyrrolo[3,2-d]pyrimidine inhibitors.
• To correlate structural features with inhibitor potency and investigate the impact of specific mutations and polyglutamylation.

Main Methods:

• X-ray crystallography to determine the structures of SHMT2-inhibitor complexes.
• Enzyme kinetic analysis and cell-based assays (HCT116) to evaluate inhibitor potency and cellular effects.
• Structure-activity relationship (SAR) analysis of inhibitor variations (bridge length, aromatic ring, polyglutamylation).

Main Results:

• Identified 5-carbon bridge length as a key determinant of pyrrolo[3,2-d]pyrimidine inhibitor potency against SHMT2.
• Demonstrated that mutation of Tyr105 in SHMT2 enhances inhibitor potency and cellular growth inhibition.
• Provided the first structural insights into the interaction of polyglutamylated antifolates with human SHMT2.

Conclusions:

• The study elucidates critical structural determinants for SHMT2 binding by pyrrolo[3,2-d]pyrimidine antifolates.
• Findings support the development of these compounds as novel antitumor agents, highlighting the importance of bridge length and specific amino acid interactions.
• Structural characterization of polyglutamylated antifolate interactions with SHMT2 offers new avenues for drug design.