Table 1.

Position of the missense mutations affecting the sensitivity of ATCase to UTP.

Mutants	Domain
Arg1076 →Ser
Asn1094 →Asp
Tyr1096 →Cys	CPSase
Trp1112 →Leu
Asp1220 →Tyr
Phe1924 →Val
Glu1933 →Lys
Glu1933 →Gly
Glu2052 →Lys
Gly2055 →Ser	ATCase
Asn2058 →Asp
Asn2157 →Lys
Glu2182 →Lys
Asp2186 →Asn

All the mutants carry missense mutations leading to a single amino acids replacement. Five of them are located in the CPSase domains while the others are in the ATCase domain. In these mutants, ATCase is no longer inhibited by UTP although CPSase retains full sensitivity to this effector.