Unveiling the Secrets of Bacterial Cell Division: A Revolutionary Discovery
In a groundbreaking revelation, a research team led by UAB's David Reverter has unraveled the intricate molecular mechanism governing bacterial cell division. This discovery, published in Nature Communications, sheds light on the process that regulates cell division in bacteria, focusing on the binding of the MraZ protein to the dcw gene cluster.
Cell division, a fundamental process for all life forms, involves the coordinated efforts of numerous proteins and regulatory elements. In most bacteria, this intricate dance is choreographed by a gene cluster known as the dcw operon. This cluster houses the genetic instructions for producing the proteins essential for cell division and bacterial wall formation.
The activation of these gene sets is orchestrated by transcription factors, proteins that bind to the promoter region of genes. This region, like a starting gate, signals the beginning of transcription, just before the first codon that encodes the protein sequence. One such crucial transcription factor is MraZ, the first gene of the dcw operon in all bacteria.
When MraZ is activated, it sets off a chain reaction, producing the necessary proteins encoded within the operon's genes, enabling bacteria to divide. Thus, MraZ acts as the master regulator, controlling the activity of the operon responsible for cell division in most bacteria.
The UAB research team, under the leadership of David Reverter, a full professor in the Department of Biochemistry and Molecular Biology and a researcher at the Institute of Biotechnology and Biomedicine of the UAB (IBB-UAB), has unveiled the intricate mechanism that regulates this vital process. Employing structural biology techniques such as X-ray crystallography and cryo-electron microscopy, the UAB team has deciphered the molecular mechanism that describes how the MraZ transcription factor binds to the promoter of the dcw operon in the bacterium Mycoplasma genitalium.
The promoter of the dcw operon is composed of four "boxes" of six nucleotides, with repeated sequences that act as regulators of transcription. By utilizing cryo-electron microscopy, the researchers were able to observe, almost at an atomic level, the specific contacts between the MraZ factor and the bases of the four repeated "boxes" of the dcw operon. This direct observation revealed a surprising finding: for the MraZ protein to bind to the operon, a distortion in its structure is necessary.
"This observation is truly remarkable. The MraZ protein, an octamer formed by eight identical subunits joined in a donut shape, has a curvature that would seemingly prevent its union with the four 'boxes' of the promoter. Yet, to regulate cell division, we witness the donut breaking and deforming in a way that allows four of its subunits to bind to the four boxes of the promoter," David Reverter explains.
This direct observation of the interactions between MraZ and the promoter DNA, which initiates cell division, represents a significant advancement in our understanding of this process. Previous attempts to decipher the mechanism relied solely on biochemical studies and computer modeling, but this research provides a more detailed and accurate picture.
Furthermore, the regulatory mechanism discovered by the UAB researchers is not limited to a specific species. "It is universal to most bacteria because all MraZ proteins are very similar, share the same octamer structure, and the DNA sequences of the promoters of the operons that regulate cell division are also similar," Reverter concludes.
This study, published in Nature Communications, was a collaborative effort led by David Reverter's research group from the Institute of Biotechnology and Biomedicine and the Department of Biochemistry and Molecular Biology of the UAB, with contributions from the ALBA synchrotron and the cryo-electron microscopy service of the Institute of Genetics and Molecular and Cellular Biology of Strasbourg, France.
