TABLE 2.

Pairs of double Cys substitutions tested for cross-linking between ends of the 3-4 loop

+ indicates cross-link formed after M2M treatment; 0 indicates cross-link not formed after M2M treatment.

Residues at N terminus of loop	Residues at C terminus of loop
	202	203	204	205	206	207	208
155					0	0	0
157	0	+a	0
158	0	0	0	0
159	0	0	0	0
160	0	+	0	+
161	+	+	0	+
163		0	0
165	+	0

^a+ indicates cross-link formed after M4M treatment but not after M2M treatment.