[RNA polymerase as a molecular machine]

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Context:

• DNA-dependent RNA polymerase is a crucial molecular machine responsible for transcription.
• Understanding the precise mechanism of its movement along DNA is fundamental to molecular biology.
• Previous models often invoked mechanical energy, which is debated at the molecular scale.

Purpose:

• To propose a novel mechanism for the directional movement of DNA-dependent RNA polymerase.
• To explain the role of Brownian motion and thermal fluctuations in molecular machine function.
• To elucidate the sequence of events driving RNA polymerase translocation.

Summary:

• This study posits that DNA-dependent RNA polymerase functions as a conveying molecular machine driven solely by Brownian motion and thermal energy.
• Mechanical energy or "power-stroke" mechanisms are considered unlikely for its conveying function.
• The proposed "Brownian ratchet mechanism" involves substrate binding and chemical reactions inducing conformational changes, which, coupled with thermal motion, ensure directional translocation along the DNA template.
• The core scheme involves substrate binding, conformational fixation, chemical reaction, alternative conformational fixation, and product-template duplex translocation.

Impact:

• Provides a new perspective on the fundamental principles governing molecular machine operation.
• Offers a plausible biophysical model for RNA polymerase translocation, potentially applicable to other molecular motors.
• Highlights the significance of thermal fluctuations and substrate-induced conformational changes in biological processes.