# A novel multifunctional role of diverse substrate binding and import by the Haemophilus Sap transporter

> **NIH NIH R01** · RESEARCH INST NATIONWIDE CHILDREN'S HOSP · 2022 · $467,483

## Abstract

Abstract
Nontypeable Haemophilus influenzae (NTHI) is a Gram-negative nasopharyngeal commensal microbe, and
opportunistic pathogen that mediates human airway diseases such as otitis media (OM), acute sinusitis,
chronic bronchitis, pneumonia, and exacerbations in patients with cystic fibrosis and chronic obstructive
pulmonary diseases. Commensals must adapt to various microenvironmental cues for long-term colonization
of the host. Disruption of commensal-host homeostasis however, can potentiate disease development.
Pathogenesis is a multifactorial and dynamic process that begins with NTHI migration to a privileged site and
culminates with bacterial growth. Growth is dependent upon multiple complex and coordinated interactions
between the microbe(s), the varied microenvironments encountered, and interactions with host immune
effectors. Bacterial strategies to thwart innate immune mechanisms and acquisition of essential nutrients are
critical for NTHI pathogenesis. The goals of my laboratory are to advance our understanding of NTHI
commensal and pathogenic behaviors, determine host microenvironmental cues that dictate these behaviors,
and target mechanisms of pathogenesis for development of novel therapies to treat disease. We defined an
essential role for the sensitivity to antimicrobial peptide (Sap) transporter in the ability of NTHI to counter the
lethal effects of host-derived antimicrobial peptides (AMPs). This novel mechanism of AMP recognition, import
and bacterial cytoplasmic degradation is essential for NTHI to counter host AMP lethality in vivo. Additional
data from our laboratory support a multi-functional role(s) for Sap transport activity, including the acquisition of
essential heme-iron. These data support the first description of an ABC transporter to import more than one
diverse substrate. Further, evidence indicates that differential assembly of Sap transporter complex proteins
dictates these unique physiological functions. We therefore hypothesize that Sap transporter permease and
ATPase proteins coordinate assembly of unique complexes to drive energetic import of AMP molecules, and
that this functional complex differs from that assembled for import of additional substrates (heme-iron). We
propose to differentiate the AMP and heme binding sites in the periplasmic binding protein, SapA, by point
mutant analysis and determine how SapA uses the binding pocket to recognize structurally diverse AMPs (Aim
1). We will define the molecular mechanisms of complex assembly, kinetics of substrate transport, and
investigate a role for these processes in bacterial nutrition (Aim 2). As part of both aims we will validate the
impact of differential substrate acquisition on NTHI persistence in the preclinical model of OM. These studies
will provide the necessary information for future studies to assess bacterial adaptation in response to these
microenvironmental cues in vivo and to design small molecule peptide inhibitors or molecules to block Sap...

## Key facts

- **NIH application ID:** 10343697
- **Project number:** 5R01AI139519-04
- **Recipient organization:** RESEARCH INST NATIONWIDE CHILDREN'S HOSP
- **Principal Investigator:** Kevin M Mason
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $467,483
- **Award type:** 5
- **Project period:** 2019-03-01 → 2024-02-29

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10343697

## Citation

> US National Institutes of Health, RePORTER application 10343697, A novel multifunctional role of diverse substrate binding and import by the Haemophilus Sap transporter (5R01AI139519-04). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10343697. Licensed CC0.

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