進化実験系の解析･評価技術･適応歩行技術の研究 : 中立ネットワークの探査と進化戦略の検討

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Considering that many amino acid sequences that fold into a common main chain structure form a percolation network in protein sequence space, we call the network "neutral network" for the structure. The neutral evolution is regarded as a walk on the neutral network. If a network for a structure A and a network for another structure B intersect each other in a special region in a sequence space, the walker can exchange one network to another network. That is, the evolving protein can change its shape from structure A to B and vise versa by accepting several mutations. Schultes et al. confirmed the existence of the neutral paths in the RNA sequence space in their experiment (Schultes & Bartel, 2000). For four distinct target structures (α, β, α/β and α+β-types ) with the same chain length of 108, we investigated whether there is the corresponding neutral network in the sequence space by using computer simulation. An exploring walk simulation suggested that the neutral network spans over the sequence space. Through another exploring walk simulation, we investigated contiguous regions between or among the neutral networks for the distinct protein structures and obtained the results that the closest approach distance between the two neutral networks ranged from 5 to 29 on the Hamming distance scale.
埼玉大学地域共同研究センターの論文