NADP and NAD utilization in Haemophilus influenzae

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Many bacteria utilize exogenous NAD and NADP to manage NAD turnover, reducing energy-intensive de novo synthesis.
• The genus Haemophilus comprises significant pathogens requiring NAD as a vital growth factor, yet NAD uptake mechanisms are not fully elucidated.
• Understanding these pathways is crucial for developing targeted antimicrobial strategies against Haemophilus species.

Purpose of the Study:

• To investigate the molecular mechanisms of NAD and NADP utilization in the genus Haemophilus.
• To identify and characterize the specific bacterial proteins involved in cofactor uptake and processing.
• To understand the role of these proteins in the growth and survival of pathogenic bacteria.

Main Methods:

• Genetic analysis of Haemophilus influenzae mutants lacking specific genes (hel and nadN).
• Biochemical characterization of the outer membrane lipoprotein e(P4) and the exported 5'-nucleotidase (nadN).
• Enzyme assays to determine substrate specificity and inhibition patterns of identified proteins.

Main Results:

• The hel gene product (lipoprotein e(P4)) and the nadN gene product (5'-nucleotidase) are essential for NAD and NADP utilization in Haemophilus.
• Lipoprotein e(P4) functions as an acid phosphatase with NADP as a substrate, inhibited by adenosine and NMN.
• The nadN gene product acts as an NAD-nucleotidase, hydrolyzing NAD, and both proteins are critical for growth.
• Adenosine was found to inhibit wild-type H. influenzae growth when NADP was the sole nicotinamide-ribosyl source.

Conclusions:

• The lipoprotein e(P4) and 5'-nucleotidase (NadN) are indispensable for the uptake and processing of NAD and NADP in Haemophilus.
• These findings reveal key molecular players in bacterial cofactor metabolism, offering potential targets for therapeutic intervention.
• The study elucidates essential growth requirements for pathogenic Haemophilus, contributing to our understanding of bacterial survival strategies.