ParC, a New Partitioning Protein, Is Necessary for the Active Form of ParA From Myxococcus pMF1 Plasmid.

Duohong Sheng,Jingjing Wang,Yuezhong Li,Yajie Li,Xiaojing Chen,Li Zhuo

doi:10.3389/fmicb.2020.623699

Abstract

The ParABS partitioning system, a main driver of DNA segregation in bacteria, employs two proteins, ParA and ParB, for plasmid partition. The pMF1 plasmid from Myxococcus fulvus 124B02 has a par operon encoding a small acidic protein, ParC, in addition to type I ParA and ParB homologs. Here, we show that expression of parC upstream of parA (as in the natural case), but not ectopic expression, is essential for the plasmid inheritance in Myxococcus cells. Co-expression of parC upstream of parA was determined to form a soluble ParC–ParA heterodimer at a 1:1 ratio, while individual expression of parA or co-expression of parA with ectopic parC formed insoluble ParA proteins. Purified ParA proteins alone had no ATPase activity and was easily dimerized, while mixing ParA with ParC formed the ParC–ParA heterodimer with the ATPase and polymerization activities. Fusing ParC and ParA also produced soluble proteins and some chimeras restored the ATPase activity and plasmid inheritance. The results highlight that proximal location of parC before parA is critical to realize the functions of ParA in the partition of Myxococcus plasmid pMF1 and shed light on a new mechanism to realize a protein function by two separate proteins.

Highlights

The Partitioning (Par) system exists widely in bacteria and archaea, participating in the isolation and allocation of chromosomes and plasmids into daughter cells during cell division (Ogura and Hiraga, 1983; Gerdes et al, 1985; Ebersbach and Gerdes, 2005)
We revealed that the parC gene is functionally essential for the partitioning system in Myxococcus cells
ParC and Its Location in pMF1 par Operon Are Critical for the Plasmid Partition

Summary

INTRODUCTION

The Partitioning (Par) system exists widely in bacteria and archaea, participating in the isolation and allocation of chromosomes and plasmids into daughter cells during cell division (Ogura and Hiraga, 1983; Gerdes et al, 1985; Ebersbach and Gerdes, 2005). Type Ib ParA contains only the Walker-box domain, represented as the ParA proteins in pTAR, pTP228, pB171, or pSM19035, and their auto-regulation role for Par transcription is fulfilled by the ParB proteins (Kwong et al, 2001; Mierzejewska and Jagura-Burdzy, 2012). Both Ia and Ib ParA proteins use the Walker-box domain to engage in the nucleoid to track for their partitioning functions (Vecchiarelli et al, 2010). Based on the ParB auto-regulation activity on the expression of the par genes and the ParA protein sequence similarity, the pMF1 partitioning system was suggested to be a member of the Ib type (Sun et al, 2011). Our results highlight that the proximal location of parC upstream of parA is critical to realize the functions of ParA in the partition of Myxococcus plasmid pMF1 and suggest a new protein evolution approach to realize a protein function by two separate proteins

AND DISCUSSION

MATERIALS AND METHODS

DATA AVAILABILITY STATEMENT