# Plasminogen and Plasmin: Structure and Function

> **NIH NIH R01** · UNIVERSITY OF NOTRE DAME · 2021 · $724,101

## Abstract

Project Summary
Bacterial pathogens have developed remarkable strategies to usurp host cell processes to establish infection,
evade immunity, and disseminate to distal sites in the host. A key highly evolved virulence strategy shared by
major human bacterial pathogens is the conscription of components of the host hemostasis system to assist
survival of the microorganism against host innate defenses. One important human pathogen, Gram+ Group A
Streptococcus pyogenes (GAS), is a model for employing such a tactic. There are >250 surface-expressed M-
protein (M-Prt)-based serotypes of GAS that colonize pharyngeal and skin epithelial cells, and which possess
the full range of minor-to-severe virulence. Many of these GAS strains contain highly expressed M-Prts, viz.,
PAM, that directly interact with host human plasminogen (hPg), whereas the M-Prts of some other strains (e.g.,
M1, M3) first interact with host fibrinogen (hFg), thus enabling the subsequent binding of hPg to the cells.
These GAS cells also secrete coevolved subforms of streptokinase (SK) that specifically activate GAS-bound
hPg to the serine protease, plasmin (hPm). In this manner, an active plasma inhibitor-resistant protease is
generated on GAS that participates via several mechanisms to protect GAS against host innate defenses. The
overall goal of this proposal centers on a unique combination of structural and biological studies of the
productive interactions that mediate the binding and activation of hPg on M-Prts of GAS cells in vitro, ex vivo,
and in vivo. The specific studies proposed to address this overall goal are contained in two Specific Aims, viz.,
 Specific Aim 1. (a) To use biophysical approaches, e.g., SPR, to study the in vitro binding properties of
hPg and to specific M-Prts, viz., PAM, as well as individual domains of this protein to minimize the primary
sequences needed to provide the high affinity binding of hPg to PAM; (b) to study atomic level binding and
dynamics of the PAM/hPg domains by high-resolution NMR and X-ray crystallography; and (c) to correlate the
binding data with the activation of hPg on GAS cells containing PAM and variants of this protein to assess the
nature of the productive binding of hPg to specific M-Prt domains. Hypothesis: these approaches will allow
identification of the essential structural features of PAM that facilitate the binding and activation of hPg on
specific types of GAS cells.
 Specific Aim 2. To generate and employ partially humanized mouse Pg transgenic mice, as well as
transgenic bacteria with deletions of PAM and/or SK, to examine the effects of conscription of the fibrinolytic
system on the stages of virulence of PAM-containing GAS. Hypothesis: using the knowledge gained in Aim 1,
we will be capable of rationally designing mice and bacteria with altered virulence and identify the stages in
which hPm bound to GAS exhibits its greatest effects.
 PHS Impact: A deepened understanding of the manner in which GAS interacts with the ...

## Key facts

- **NIH application ID:** 10067561
- **Project number:** 5R01HL013423-46
- **Recipient organization:** UNIVERSITY OF NOTRE DAME
- **Principal Investigator:** FRANCIS J CASTELLINO
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $724,101
- **Award type:** 5
- **Project period:** 1975-02-01 → 2022-09-18

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10067561

## Citation

> US National Institutes of Health, RePORTER application 10067561, Plasminogen and Plasmin: Structure and Function (5R01HL013423-46). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10067561. Licensed CC0.

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