M, DNA molecular weight marker. Lane 1, m6-L303S/S332P/K337E; lane 2, m7-W274C; lane 3, m7-S361P; lane 4, m12-F326S/L350F; lane 5, m12-K472E; lane 6, m13-C333S; lane 7, m15-C333R; lane 8, m15-I459V; lane 9, m17-K82R/V270M; lane 10, m17-V270M/N334D; lane 11, m17-N334D; lane 12, m27-Y181F; lane 13, m27-Y181F/V260D; lane 14, m27-V260D/L329P; lane 15, m27-L329P; lane 16, m70-Y138F; lane 17, m70-L256P; lane 18, m76-I214T/Y259C; lane 19, m76-Y259C/D278G/I289V/F363L; lane 20, m76-D278G/I289V/F363L; lane 21, wt Eco31I; lane 22, cell extract without enzyme.