Table 1. Substitutions at potential adventitious contact sites that enhanced inhibition of furin, relative to R₄R₁-eglin or R₄K₁-eglin.

Position of substitution*	Major effect†	Minor effect
R4R1 construct
Glu-39‡	nd	Pro
Gly-40‡	nd	Ala, Arg, Pro
Tyr-49	Asp	Ala
R4K1 construct
Asp-33	nd	Val

nd, none detected

^*No substitutions were found at Tyr-35, Leu-47, His-65, or His-68 (R₄R₁ context) or at Leu-37 or Asn-30 (R₄K₁ context) that enhanced affinity

^†Substitutions that exhibited a major effect (>5-fold) or a minor effect (<5-fold) on furin affinity are shown. These results are based on precise inhibition assays using purified inhibitors as described in Materials and Methods

^‡Glu-39 and Gly-40 substitutions generated temporary inhibitors for furin as described in the text