Table 1. Substrates for SfiI with altered spacer sequences.

Oligoduplexa	Nameb	Reaction velocities (mol product/mol SfiI/min)c
		At 0.2 µM substrate	At 1 µM substrate
5′-ATGTGGCCATATAGGCCTATT-3′	ATATA	1.2	1.4
3′-TACACCGGTATATCCGGATAA-5′
5′-ATGTGGCCAAAAAGGCCTATT-3′	AAAAA	9.0	38
3′-TACACCGGTTTTTCCGGATAA-5′
5′-ATGTGGCCAACAAGGCCTATT-3′	AACAA	1.9	3.0
3′-TACACCGGTTGTTCCGGATAA-5′
5′-ATGTGGCCAAACAGGCCTATT-3′	AAACA	28	204
3′-TACACCGGTTTGTCCGGATAA-5′
5′-ATGTGGCCAAAACGGCCTATT-3′	AAAAC	8.0	38
3′-TACACCGGTTTTGCCGGATAA-5′

^aSynthetic oligodeoxyribonucleotides were annealed to give the duplexes shown. The specified GGCC elements in the recognition sequence for SfiI are in bold.

^bThe oligoduplexes are named from the sequence of the 5 bp spacer in the ‘top’ strand of the SfiI site. Top and bottom strands refer to the orientations shown here.

^cReaction velocities were measured as in Figure 2, from reactions in SfiI assay buffer at 30°C that contained one of the oligoduplexes (5′-end-labelled with ³²P in the top strand) at the concentrations indicated and SfiI endonuclease at a 400-fold lower concentration (except for the reactions on AAACA where the nuclease was at a 2000-fold lower concentration).