Page 74 - MI-1-1

Microbes & Immunity

ORIGINAL RESEARCH ARTICLE
An ATP-free packaging of T4 DNA

Seiko Hara*
Department of Comparative Culture, School of International Liberal Arts, Miyazaki International
University, 1405 Kano, Kiyotake-cho, Miyazaki-Shi, Miyazaki, Japan

Abstract

Packaging of viral DNA into a capsid with liquid crystalline density is a crucial step
in viral reproduction. DNA packaging with an adenosine triphosphate (ATP)-fueled
molecular motor is an established viral DNA packaging mechanism system. On
the other hand, DNA is compacted by the conformational change attributable to
multivalent cations exclusively at valences higher than three. The conformational
change of DNA was not considered as a mechanism of DNA packaging of viruses.
Here, T4 DNA, ejected from a capsid in the ambient concentration of phosphate
corresponding to the intra-cell concentration, is packaged into the capsid when the
phosphate concentration decreases to the extra-cell concentration in coexistence
with divalent cations, that is, Ca and Mg . The compaction and packaging processes
2+
2+
coincide with the conformational change of DNA. Divalent cations can compact T4
DNA when the counter anion is phosphate. The DNA-packaged and re-generated
virions showed equivalent infective ability with the original populations. Fluorescent
microscopy distinguished the conformational changes of DNA between compact
forms and coil forms. Packaged or unpackaged DNA was confirmed enzymatically.
Plaque-forming unit (Pfu) was used as the measure of infectious ability of virions. The
concentration of ATP was measured by the luminometric method. The packaging
process was proceeded in picomolar or lower concentration of ATP. This series of
*Corresponding author: procedures may constitute a new ATP-free or low-ATP approach to packaging viral
Seiko Hara
(shara.laofu@gmail.com) DNA with DNA conformational change underpinning the process. The results from
this study may disclose an undiscovered facet of T4 life cycle.
Citation: Hara S. An ATP-free
packaging of T4 DNA. Microbes &
Immunity. 2024;1(1):2666. Keywords: Divalent cation; Calcium; Phosphate; Compaction; Conformational change
doi: 10.36922/mi.2666
Received: January 7, 2024
Accepted: February 27, 2024
1. Introduction
Published Online: March 19, 2024
Bacteriophage T4 is among the most intensively studied viruses, with its life cycle
Copyright: © 2024 Author(s).
1
This is an Open-Access article constantly being a subject of rigorous investigation. It is generally agreed that packaging
distributed under the terms of the of a long and self-repulsive string of phage DNA into a small empty capsid as liquid
Creative Commons Attribution crystalline DNA requires an energy-consuming molecular motor. In the metabolism
2
3,4
License, permitting distribution,
and reproduction in any medium, of T4, no net packaging of DNA into the capsid was observed at concentrations of
provided the original work is adenosine triphosphate (ATP) under 25 μM. The energy stored in the highly pressurized
5
properly cited. DNA is used as the force for ejection of the DNA into the host. This implies that the
2,6
Publisher’s Note: AccScience DNA packaged in a capsid takes a random coil structure, and the self-repulsive DNA
Publishing remains neutral with fiber is arranged irregularly in the capsid. On the other hand, a cryoelectron micrograph
regard to jurisdictional claims in 7
published maps and institutional of a viral head has revealed a regularly spaced arrangement of intra-capsid DNA. A
affiliations. mechanism to reconcile these contradictory conditions is anticipated.
Volume 1 Issue 1 (2024) 68 doi: 10.36922/mi.2666