STX1A and hemolytic-uremic syndrome: On the other hand, Stx2 is known to be more involved in complications of HUS than Stx1 [47], probably due to the fact that its A1 subunit has a higher affinity for ribosomes and a higher catalyzing potency than A1 subunit of Stx1, which makes it more cytotoxic than Stx1 [48].