Table 1.

Mutational alterations identified from the sequence analysis of heat-stable mutants

	Mutation
Sh2hs13	Ala to Pro at position 177
Sh2hs14	Asp to His at position 400
	Val to Ile at position 454
Sh2hs16	Arg to Thr at position 104
Sh2hs33	His to Tyr at position 333
Sh2hs39	His to Tyr at position 333
Sh2hs40	His to Tyr at position 333
	Thr to Ile at position 460
Sh2hs47	Arg to Pro at position 217
	His to Tyr at position 333

The His-to-Tyr mutation was identified in four of the seven variants analyzed either alone or in combination with a second mutation.