Table 2.

Functionally important residues in MmoX vs. IsoA, mapped according to Methylosinus trichosporium Ob3b (MmoX) and Rhodococcus sp. AD45 (IsoA) sequence numbering. Note: The functional roles of IsoA residues are putative, based solely on in silico structural and sequence homology with MmoX (PDB 1MTY). These predicted correspondences identify candidate positions for future site-directed mutagenesis to verify catalytic and structural roles within the IsoMO di-iron centre.

Residue function	MmoX	IsoA
Gating	L110	L101
Enantioselectivity	G113, G208	G104, V202
Important in methane oxidation	C151, M184, F282	D147, V178, F274
Highly conserved	T213	T207
Iron ligand	E114, E144, H147, E209, E243, H246	E110, E140, H143, E203, E237, H240
Hydrogen bonding between C and F helices	D143, R146, S238, D242, R245	D139, R142, S232, D236, R239
Access of substrates and release of products to and from the active site	T213, N214, E240	T207, N208, Q234
Tightly packed regions of the protein	A117, G250	A113, G244
Canyon	Y67, K74, L321, G325, P329	Y64, K71, G315, P319
Handle	A224, G228, D229	A218, G222, D223
Possible docking	Y292, W371, Y376, P377	Y284, W362, Y367, P368
Interact with gamma	P424, G443, P461, Y464	P408, G427, Y430