Populations of different loop conformations.

a The center-of-mass distance between alpha carbons of four loop residues (100–103) and those of Tyr238 and Lys242, which reside on the opposite side of the binding groove, was used to define loop conformations: distance smaller than 0.9 nm, closed; larger than 1.05 nm, open; between 0.9 nm and 1.05 nm, intermediate.b Only monomers with the mobile loop initially closed are considered.a 本研究以位于结合槽（binding groove）对侧的4个环残基（loop residues，100–103位）的α碳原子（alpha carbon）与Tyr238、Lys242的α碳原子之间的质心距离，对环构象进行界定：当该距离小于0.9 nm时为闭合态，大于1.05 nm时为开放态，介于0.9 nm与1.05 nm之间时为中间态。 b 本研究仅纳入初始状态下可动环（mobile loop）呈闭合态的单体（monomer）。