Protein Allostery Calculator

Protein Allostery Calculator is a free, scientifically accurate online tool designed to help researchers, students, and biochemists quantify allosteric behavior in proteins using the gold-standard Monod-Wyman-Changeux (MWC) concerted model and Hill equation analysis.

What is Protein Allostery?

Protein allostery refers to the regulation of a protein’s activity by binding of an effector molecule at a site other than the active site. This phenomenon, first described by Monod, Wyman, and Changeux in 1965, is fundamental to biological regulation. Classic examples include hemoglobin, aspartate transcarbamoylase, and many enzymes and receptors.

Why Use the Protein Allostery Calculator?

Understanding allostery is critical in drug discovery, enzyme engineering, and systems biology. This Protein Allostery Calculator implements the authentic MWC two-state model and calculates key parameters such as:

• Allosteric constant L (T₀/R₀ ratio)
• Affinity ratio c (K_R / K_T or K_T / K_R)
• Hill coefficient (n_H)
• Fractional saturation (Y) with and without effector
• Allosteric effector impact (activation or inhibition)

Scientific Foundation

The calculator strictly follows the peer-reviewed Monod-Wyman-Changeux (MWC) model published in Journal of Molecular Biology (1965). The fractional saturation in the absence and presence of allosteric effector is calculated using:

Y = [ [S]/K_R × (1 + [S]/K_R)^n-1 + L × c × [S]/K_R × (1 + c × [S]/K_R)^n-1 × (1 + [A]/K_A)^m ] / [ (1 + [S]/K_R)ⁿ + L × (1 + c × [S]/K_R)ⁿ × (1 + [A]/K_A)^m ]

When Should You Use This Tool?

Use the Protein Allostery Calculator when:

• Analyzing oxygen binding curves of hemoglobin or myoglobin mutants
• Characterizing allosteric enzymes (e.g., phosphofructokinase, ATCase)
• Evaluating drug candidates that act as allosteric modulators
• Teaching allostery and cooperativity in biochemistry courses
• Fitting experimental saturation or velocity data to extract L and c

User Guidelines

1. Enter the number of subunits (n) and effector binding sites (m)
2. Input dissociation constants (K_R, K_T, K_A) in µM or nM
3. Provide the allosteric constant L (typically 10²–10⁶)
4. Enter substrate [S] and effector [A] concentrations
5. Click “Calculate” to get instant results with interpretation.

The tool automatically computes cooperativity (Hill coefficient), shift in affinity, and classifies the effector as activator (c < 1) or inhibitor (c > 1).

Protein allostery is one of the most elegant regulatory mechanisms in nature. From the sigmoidal oxygen binding of hemoglobin that enables efficient oxygen delivery, to feedback inhibition in metabolic pathways, allosteric proteins are central to life. This calculator brings decades of biophysical research directly to your browser with zero installation.

Whether you're a graduate student fitting binding isotherms, a professor preparing lecture material, or a drug discovery scientist screening allosteric modulators, the Protein Allostery Calculator delivers publication-quality results instantly and for free.