Event Title

Exploring the Link Between Iron Homeostasis and PhpP Activity

Session Title

STEM and Biomedical Research

Presenter Information

David BrandyburgFollow

Document Type

Oral Presentation

Faculty Mentor

Nicholas Grossoehme, Ph.D.

College

College of Arts and Sciences

Department

Department of Chemistry, Physics, and Geology

Description

RitR (repressor of iron transport) is an orphan two-component signal transduction response regulator in Streptococcus pneumoniae that is central to iron homeostasis. RitR, however, lacks the amino acid (aspartic acid) that serves as the phosphate acceptor in traditional response regulators – consequently, it does not function in the same way that other response regulators do. Since its discovery, it has been shown that this protein is indeed the target of a Ser-Thr kinase-phosphatase pair, StkP and PhpP. STK has been shown to phosphorylate RitR in response to extracellular iron. This phosphorylation impacts the DNA binding ability of RitR, leading to expression of iron uptake genes. PhpP is an intercellular phosphatase that hydrolyzes the phosphate and effectively reverses the signal. This project aimed to determine whether PhpP could be metal sensitive and, if so, to test the sensitivity. This was accomplished using a standard pNPP (para-nitrophenylphosphate) assay. By utilizing this assay, we were able to determine that PhpP is indeed capable of dephosphorylating a chemical substrate and does so in an iron-dependent manner. Steps were taken to develop an assay to monitor the hydrolysis of phospho-RitR; however, optimization is still necessary.

Previously Presented/Performed?

Summer Undergraduate Research Experience (SURE) Poster Session, Winthrop University, October 2019

Grant Support?

Supported by an SC INBRE grant from the National Institute for General Medical Sciences (NIH-NIGMS)

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Apr 24th, 12:00 AM

Exploring the Link Between Iron Homeostasis and PhpP Activity

RitR (repressor of iron transport) is an orphan two-component signal transduction response regulator in Streptococcus pneumoniae that is central to iron homeostasis. RitR, however, lacks the amino acid (aspartic acid) that serves as the phosphate acceptor in traditional response regulators – consequently, it does not function in the same way that other response regulators do. Since its discovery, it has been shown that this protein is indeed the target of a Ser-Thr kinase-phosphatase pair, StkP and PhpP. STK has been shown to phosphorylate RitR in response to extracellular iron. This phosphorylation impacts the DNA binding ability of RitR, leading to expression of iron uptake genes. PhpP is an intercellular phosphatase that hydrolyzes the phosphate and effectively reverses the signal. This project aimed to determine whether PhpP could be metal sensitive and, if so, to test the sensitivity. This was accomplished using a standard pNPP (para-nitrophenylphosphate) assay. By utilizing this assay, we were able to determine that PhpP is indeed capable of dephosphorylating a chemical substrate and does so in an iron-dependent manner. Steps were taken to develop an assay to monitor the hydrolysis of phospho-RitR; however, optimization is still necessary.