Table 1. Mutations for each round of protein engineering.

Cre mutant	Mutations
Cre–A1	K25R, D29R, R32E, D33L, Q35R
Cre–B1	E69D, R72K, L76E
Cre–A2	Cre–A1 + R337E
Cre–B2	Cre–B1 + E308R
Cre–A3	Cre–A2 + E123L