Structural Basis of Nucleotide Selectivity in Pyruvate Kinase.

Area of Science:

• Biochemistry
• Molecular Biology
• Microbiology

Background:

• Nucleoside triphosphates are vital for cellular processes, with their synthesis enzymes playing key roles in cell proliferation.
• Pyruvate kinase (PYK), typically known as a terminal glycolytic enzyme, also synthesizes various nucleoside triphosphates.

Purpose of the Study:

• To elucidate the structural basis for nucleotide selectivity in pyruvate kinase.
• To investigate the mechanism underlying Streptococcus pneumoniae PYK's preference for GTP synthesis.

Main Methods:

• X-ray crystallography was used to determine the structures of Streptococcus pneumoniae PYK bound to four different nucleotides.
• Comparative analysis of protein-nucleotide interactions was performed.

Main Results:

• Crystal structures revealed specific interactions enabling PYK to differentiate nucleotide bases.
• A conserved sequence motif in the nucleotide recognition site was identified as crucial for GTP synthesis selectivity.
• PYK variants with impaired GTP/UTP synthesis showed compromised pneumococcal cell growth.

Conclusions:

• The study provides structural insights into PYK's nucleotide synthesis and selectivity.
• PYK plays a critical role in maintaining nucleotide homeostasis in prokaryotes.
• Findings advance understanding of PYK biochemistry and prokaryotic metabolism.