Moonlighting in Bacillus subtilis: The Small Proteins SR1P and SR7P Regulate the Moonlighting Activity of Glyceraldehyde 3-Phosphate Dehydrogenase A (GapA) and Enolase in RNA Degradation.

Sabine Brantl,Inam Ul Haq

doi:10.3390/microorganisms9051046

Sabine Brantl, Inam Ul Haq

Open Access

https://doi.org/10.3390/microorganisms9051046

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Journal: Microorganisms	Publication Date: May 12, 2021
Citations: 8	License type: CC BY 4.0

Affiliation: Friedrich Schiller University Jena

Abstract

Moonlighting proteins are proteins with more than one function. During the past 25 years, they have been found to be rather widespread in bacteria. In Bacillus subtilis, moonlighting has been disclosed to occur via DNA, protein or RNA binding or protein phosphorylation. In addition, two metabolic enzymes, enolase and phosphofructokinase, were localized in the degradosome-like network (DLN) where they were thought to be scaffolding components. The DLN comprises the major endoribonuclease RNase Y, 3′-5′ exoribonuclease PnpA, endo/5′-3′ exoribonucleases J1/J2 and helicase CshA. We have ascertained that the metabolic enzyme GapA is an additional component of the DLN. In addition, we identified two small proteins that bind scaffolding components of the degradosome: SR1P encoded by the dual-function sRNA SR1 binds GapA, promotes the GapA-RNase J1 interaction and increases the RNase J1 activity. SR7P encoded by the dual-function antisense RNA SR7 binds to enolase thereby enhancing the enzymatic activity of enolase bound RNase Y. We discuss the role of small proteins in modulating the activity of two moonlighting proteins.

Highlights

Moonlighting proteins are proteins with more than one function
As Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is an abundant protein required for glycolysis in all organisms, it is not excluded that it moonlights in RNA degradation in other bacteria, too
When we searched for new targets of the 205-nt long trans-encoded sRNA SR1 which is expressed under gluconeogenic conditions and repressed by CcpN and CcpA under glycolytic conditions [7], we found that SR1 is a dual-function sRNA: it acts as base-pairing sRNA in arginine catabolism [50,51], but is an mRNA that encodes a 39 aa small protein, which we designated SR1P [8,10]

Summary

Introduction

Moonlighting proteins are proteins that exhibit more than one function (rev. in [1]). GAPDH proteins, and, surprisingly, did exhibit GAPDH enzymatic activity, but was bound to lysozyme, cytoskeletal proteins and fibronectin [2] Four years later, another group identified S. pyogenes GAPDH as a cell surface receptor for plasminogen [3]. We have discovered two small proteins, SR1P and SR7P, that bind the glycolytic enzymes GapA (one of the two GAPDHs) and Eno, respectively. Microorganisms 2021, 9, 1046 was already known to act as scaffolding protein in the hypothetic B. subtilis degradosome [6], an additional activity in RNA degradation was not known before for GapA. It was unexpected that the second small protein discovered and further characterized by our group, SR7P, which is encoded by a dual-function antisense RNA, interacts with Eno [11]. We will first provide an overview of four types of moonlighting proteins found in B. subtilis and afterwards focus on GapA and Eno and the modulation of their moonlighting function by two small proteins

Moonlighting Proteins in Bacillus Subtilis Known until 2015

The Aconitase CitB Moonlights as RNA Binding Protein

The Glucose Permease PtsG Phosphorylates the RNA Binding Protein GlcT

Other Moonlighting Proteins

Interactions

GapA–SR1P

The Small Protein SR1P Impacts the Moonlighting Activity of GapA

Eno–SR7P

The Small Protein SR7P Modulates the Moonlighting Activity of Enolase

Conclusions