Aminocarboxypropyltransferase that catalyzes the aminocarboxypropyl transfer on pseudouridine corresponding to position 914 in M.jannaschii 16S rRNA. It constitutes the last step in biosynthesis of the hypermodified N1-methyl-N3-(3-amino-3-carboxypropyl) pseudouridine (m1acp3-Psi). an N(1)-methylpseudouridine in 16S/18S rRNA + S-adenosyl-L-methionine = H(+) + N(1)-methyl-N(3)[(3S)-3-amino-3-carboxypropyl]pseudouridine in 16S/18S rRNA + S-methyl-5'-thioadenosine Belongs to the TDD superfamily. TSR3 family.