Water-Mediated Energy Dynamics in a Homodimeric Hemoglobin

Area of Science:

• Biophysics
• Structural Biology
• Biochemistry

Background:

• Hemoglobin (HbI) from Scapharca inaequivalvis is a homodimeric protein exhibiting cooperativity.
• Ligand binding and dissociation in HbI involve a water molecule cluster at the protein interface.
• Understanding HbI's energy dynamics is key to elucidating its allosteric mechanisms.

Purpose of the Study:

• To investigate energy dynamics in both unliganded and liganded states of Scapharca inaequivalvis hemoglobin (HbI).
• To analyze the role of the interface water cluster and specific salt bridges in HbI's energy transport and cooperativity.

Main Methods:

• Construction and analysis of a dynamic network model representing residues, hemes, and water clusters.
• Identification of nonbonded networks (NBNs) to map rapid responses to local protein strain.
• Analysis of energy transport times and nonbonded interactions within HbI.

Main Results:

• Two major nonbonded networks (NBNs) were identified: one involving the Lys30-Asp89 salt bridge and another including hemes, surrounding residues, and the interface water cluster.
• Energy transport is significantly influenced by the Lys30-Asp89 salt bridge and the interface water cluster in the unliganded state.
• The identified networks and energy transport pathways provide insights into local strain responses within HbI.

Conclusions:

• The Lys30-Asp89 salt bridge and the interface water cluster are critical regulators of energy transport in HbI.
• These findings suggest a direct link between local strain responses, energy dynamics, and the allosteric transitions observed in HbI.
• The study provides a novel network-based approach to understanding protein dynamics and function.