TABLE 4.

Summary of the effects of the mutations investigated in this study^a

Mutationb	Secretion from ETEC		Secretion from V. cholerae
	LT	CTB	CTB	LTB
Q3K	Reduced	Wild type	Wild type	Not detectedd
Q3A	Wild type	—c	—	Not detected
E11K	Reduced	Wild type	Reduced	Little detected
E11A	Near wild type	Wild type	Reduced	—
L25E	Reduced	—	—	Wild typee

^aData shown characterize levels in cell-free supernatant, as measured by G_M1 ELISA.

^bAll mutations are in the B subunit; the LT holotoxin was expressed in ETEC.

^c—, not tested.

^dNo mutant LTB could be detected in total culture samples by immunoblotting.

^eSecreted LTB[L25E] is readily detectable in the cell-free supernatant by immunoblotting.