Structure of GroEL in complex with an early folding intermediate of alanine glyoxylate aminotransferase.
Primary hyperoxaluria type 1 is a rare autosomal recessive disease caused by mutations in the alanine glyoxylate aminotransferase gene (AGXT). We have previously shown that P11L and I340M polymorphisms together with I244T mutation (AGXT-LTM) represent a conformational disease that could be amenable to pharmacological intervention. Thus, the study of the folding mechanism of AGXT is crucial to understand the molecular basis of the disease. Here, we provide biochemical and structural data showing that AGXT-LTM is able to form non-native folding intermediates. The three-dimensional structure of a complex between the bacterial chaperonin GroEL and a folding intermediate of AGXT-LTM mutant has been solved by cryoelectron microscopy. The electron density map shows the protein substrate in a non-native extended conformation that crosses the GroEL central cavity. Addition of ATP to the complex induces conformational changes on the chaperonin and the internalization of the protein substrate into the folding cavity. The structure provides a three-dimensional picture of an in vivo early ATP-dependent step of the folding reaction cycle of the chaperonin and supports a GroEL functional model in which the chaperonin promotes folding of the AGXT-LTM mutant protein through forced unfolding mechanism.
Albert
Armando
A
Grupo de Cristalografía Macromolecular y Biología Estructural, Instituto de Química Física Rocasolano, Consejo Superior de Investigaciones Científicas, Madrid E-28006, Spain. xalbert@iqfr.csic.es
Yunta
Cristina
C
Arranz
Rocío
R
Peña
Alvaro
A
Salido
Eduardo
E
Valpuesta
José María
JM
Martín-Benito
Jaime
J
D000255:Adenosine Triphosphate / Q000494:pharmacology; D001426:Bacterial Proteins; D018834:Chaperonin 60 / Q000737:chemistry*; D018833:Chaperonins / Q000737:chemistry; D020285:Cryoelectron Microscopy; D006801:Humans; D006960:Hyperoxaluria, Primary / Q000201:enzymology / Q000235:genetics; D020125:Mutation, Missense; D011110:Polymorphism, Genetic; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D000637:Transaminases / Q000737:chemistry* / Q000235:genetics
D001426:Bacterial Proteins; D018834:Chaperonin 60; D000255:Adenosine Triphosphate; D000637:Transaminases; C019635:Alanine-glyoxylate transaminase; D018833:Chaperonins