Table 2.

B. subtilis mutL missense mutation conserved in human MLH1^a

B. subtilis mutL missense mutation	Human MLH1 missense mutation	No. of reported occurrences in humansb	Potential functionc
A17V	A21V	6	ATP binding
G18A	G22A	11	ATP binding
P24L	P28L	32	ATP hydrolysis
E30A	E34A	4	ATP hydrolysis
N34H	N38H	8	ATP hydrolysis
S40A	S44A	5	ATP hydrolysis
N60S	N64S	20	Unclear
G63R	G67R	74	ATP binding
K80E	K84E	20	ATP hydrolysis
G94S	G98S	8	ATP binding
S102R	S106R	7	ATP binding
R176G	R182G	14	DNA binding
G234V	G244V	6	DNA binding
R256C	R265C	53	ATP binding

^aA list of MLH1 mutations, the corresponding B. subtilis missense mutations, the reported incidence in HNPCC patients, and the possible MutL functions impaired by each mutation is shown.

^bThe occurrence of each human MLH1 missense mutation was obtained from the International Society for Gastrointestinal Tumors (www.insight-group.org).

^cPotential function refers to the predicted biochemical function affected by each mutation based on the corresponding missense mutation location in S. cerevisiae Mlh1 or E. coli MutL where the biochemical defect has been determined (2, 26).