# Cell surface polymer display in Gram-positive bacteria

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2021 · $448,026

## Abstract

Project Summary
Pathogenic bacteria display polymeric virulence factors to establish and maintain infections. We will investigate
the mechanisms through which these polymers are produced and search for small molecule polymer assembly
inhibitors. Two types of surface polymers in Gram-positive bacteria will be studied, (i) pili, proteinaceous fibers
that project from the cell surface to mediate adhesion to host tissues, and (ii) Wall Teichoic Acids (WTAs), highly
abundant glycopolymers that play a fundamental role in maintaining the integrity of the cell wall. Both pili and
WTA polymers are important virulence factors, but how they are synthesized is poorly understood. In aims #1-
2, we will study how the archetypal SpaA-pilus from Corynebacterium diphtheria is assembled by sortase
polymerases. These enzymes catalyze a unique transpeptidation reaction that covalently links adjacent protein
pilus subunits together via a lysine isopeptide bond, thereby conferring enormous tensile strength that enables
bacterial adherence. By synergistically employing structural, biochemical, cellular and chemical tools, we will
learn how sortase polymerases build the pilus shaft and define the structure of the fundamental building block
from which all Gram-positive pili are constructed. We will also determine the molecular basis through which pilus
biogenesis is terminated via a novel handoff mechanism in which the pilus is transferred between tandemly
arranged sortases on the cell surface. This work will have a broad impact, as a wide range of pathogenic
microbes use a similar mechanism to assemble their pili. In aim #3, we will study how Gram-positive bacteria
produce WTA using the TarA enzyme, a novel glycosyltransferase that catalyzes the first committed step in
polymer biosynthesis. TarA is a promising drug target, as clinically relevant methicillin-resistant Staphylococcus
aureus (MRSA) is defective in host colonization and re-sensitized to Beta-lactam drugs when WTA biosynthesis
is disrupted. Crystal structures of TarA in its apo- and substrate-bound forms will be determined, facilitating the
rational exploration of its catalytic mechanism. High-throughput screening using a novel, cell-based bacterial
cytological profiling assay will also be performed to discover small molecule TarA inhibitors that could have useful
therapeutic properties. Combined, studies of pilus and WTA biogenesis will provide fundamental insight into the
chemistry underlying polymer assembly in Gram-positive bacteria and could lead to novel antibiotics to treat
infections caused by MRSA and other multi-drug resistant bacteria.

## Key facts

- **NIH application ID:** 10151608
- **Project number:** 5R01AI052217-19
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Robert Thompson Clubb
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $448,026
- **Award type:** 5
- **Project period:** 2002-06-01 → 2023-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10151608

## Citation

> US National Institutes of Health, RePORTER application 10151608, Cell surface polymer display in Gram-positive bacteria (5R01AI052217-19). Retrieved via AI Analytics 2026-06-10 from https://api.ai-analytics.org/grant/nih/10151608. Licensed CC0.

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