Processing of Cholinesterase-like alpha/beta-Hydrolase Fold Proteins: Alterations Associated with Congenital Disorders

The alpha/beta hydrolase fold family is perhaps the largest group of proteins presenting significant structural homology with divergent functions, ranging from catalytic hydrolysis to heterophilic cell adhesive interactions to chaperones in hormone production. All the proteins of the family share a common three-dimensional core structure containing the alpha/beta-hydrolase fold domain that is crucial for proper protein function. Several mutations associated with congenital diseases or disorders have been reported in conserved residues within the alpha/beta-hydrolase fold domain of cholinesterase-like proteins, neuroligins, butyrylcholinesterase and thyroglobulin. These mutations are known to disrupt the architecture of the common structural domain either globally or locally. Characterization of the natural mutations affecting the alpha/beta-hydrolase fold domain in these proteins has shown that they mainly impair processing and trafficking along the secretory pathway causing retention of the mutant protein in the endoplasmic reticulum. Studying the processing of alpha/beta-hydrolase fold mutant proteins should uncover new functions for this domain, that in some cases require structural integrity for both export of the protein from the ER and for facilitating subunit dimerization. A comparative study of homologous mutations in proteins that are closely related family members, along with the definition of new three-dimensional crystal structures, will identify critical residues for the assembly of the alpha/beta-hydrolase fold.