Size Scaling of Mutation Avalanches in a Model for Protein Evolution

✍ Scribed by DJORDJE L. NIKOLIC; DANIEL J. LACKS

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 182 KB
• Volume: 221
• Category: Article
• ISSN: 0022-5193
• DOI: 10.1006/jtbi.2003.3188

✦ Synopsis

The tunably rugged NK-model is used to study avalanche-like events that occur when environmental change causes fitness optima to disappear. The probability of an event with Delta substitutions scales as exp(-c Delta) for smooth landscapes, and as exp(-c Delta(2)) for rugged landscapes. Increasing the ruggedness leads to two competing effects: (1) more possible routes by which single mutations can increase the fitness, which dominates at low ruggedness and acts to increase Delta; and (2) a higher density of fitness optima, which dominates at high ruggedness and acts to decrease Delta. Due to these competing effects, the largest average values of Delta occur at intermediate ruggedness. The effects of system size on the avalanche events are examined, and average values of Delta increase logarithmically with system size. The variance to mean ratios for the number of substitutions per unit time are consistent with experimental results for protein evolution.