<p> The ATP-grasp fold is one of several distinct ATP-binding folds, and is found in enzymes that catalyze the formation of amide bonds, catalyzing the ATP-dependent ligation of a carboxylate-containing molecule to an amino or thiol group-containing molecule [<cite idref="PUB00020972"/>]. This fold is found in many different enzyme families, including various peptide synthetases, biotin carboxylase, synapsin, succinyl-CoA synthetase, pyruvate phosphate dikinase, and glutathione synthetase, amongst others [<cite idref="PUB00028114"/>]. These enzymes contribute predominantly to macromolecular synthesis, using ATP-hydrolysis to activate their substrates. </p><p>This entry represents the pre-ATP-grasp domain, which precedes the ATP-grasp domain in all superfamily members, and which usually occurs at the N terminus of the protein. The structure of the pre-ATP-grasp domain consists of alpha/beta/alpha in three layers, and is possibly a rudiment form of the Rossmann-fold. This domain can have a substrate-binding function.</p>