IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Monitoring acquisition of glycoprotein tertiary and quaterenary structures in the endoplasmic reticulum
Autor/es:
JJ CARAMELO OA CASTRO Y ARMANDO PARODI
Lugar:
Ashburn, Virginia, USA. Septembere 26-29 2006
Reunión:
Otro; Howard Hughes Meeting of International Research Scholar; 2006
Institución organizadora:
Howard Hughes Medical Institute
Resumen:
Monitoring acquisition of glycoprotein tertiary and quaternary structures in the endoplasmic reticulum
ARMANDO J. PARODI, Leloir Institute Foundation,Buenos Aires, ArgentinaRMANDO J. PARODI, Leloir Institute Foundation,Buenos Aires, Argentina
J.J. Caramelo, O.A. Castro, A.J. Parodi ?¡ Leloir Institute
Foundation, Buenos Aires, Argentina
Foundation, Buenos Aires, Argentina
?¡ Leloir Institute
Foundation, Buenos Aires, Argentina
?¡ Both the folding status of glycoprotein monomers and the assembly of multimeric glycoprotein
complexes are stringently controlled in the endoplasmic reticulum (ER) by a glucosyltransferase
(GT) that creates monoglucosylated structures recognized by ER-resident lectins (calnexin
and calreticulin). Monoglucosylated glycoproteinlectin interaction prevents exit to the Golgi of
structurally faulty macromolecules. Given that it only glucosylates incompletely assembled glycoprotein
multimers and glycoprotein monomers that do not display their native structures, GT serves as
a folding/assembly sensor. To explore the structural determinants for GT-mediated glucosylation, we
used as acceptor substrates a family of chemically glycosylated proteins derived from chymotrypsin
inhibitor 2. Structural characterization of species showing higher glucose acceptor capacity indicated
that GT recognizes solvent-accessible hydrophobic patches in molten globule-like conformers mimicking
glycoprotein advanced folding stages. Further,to determine if the GT-derived quality control is
operative with conformers displaying structures closely resembling those of native species and that,
therefore, no alternative ER retaining mechanisms are required when glycoproteins approach their
native folding, we generated and used as acceptor substrates neoglycoproteins bearing conformations
mimicking the very last-stage folding structures adopted by glycoproteins entering the ER lumen.
Results obtained demonstrate that GT is an exquisite sensor of glycoprotein conformations, able to
recognize folding intermediates only slightly differingfrom the native species. Finally, results obtained
using isolated subunits of a homotetrameric glycoprotein (soybean agglutinin) as acceptor substrate
showed that GT is also able to recognize hydrophobic interfaces exposed by properly folded
subunits not yet forming part of complete multimeric complexes, thus ensuring ER retention of
incompletely assembled multimeric species. The same mechanism operates, therefore, to monitor
glycoprotein acquisition of both tertiary and quaternary structures
complexes are stringently controlled in the endoplasmic reticulum (ER) by a glucosyltransferase
(GT) that creates monoglucosylated structures recognized by ER-resident lectins (calnexin
and calreticulin). Monoglucosylated glycoproteinlectin interaction prevents exit to the Golgi of
structurally faulty macromolecules. Given that it only glucosylates incompletely assembled glycoprotein
multimers and glycoprotein monomers that do not display their native structures, GT serves as
a folding/assembly sensor. To explore the structural determinants for GT-mediated glucosylation, we
used as acceptor substrates a family of chemically glycosylated proteins derived from chymotrypsin
inhibitor 2. Structural characterization of species showing higher glucose acceptor capacity indicated
that GT recognizes solvent-accessible hydrophobic patches in molten globule-like conformers mimicking
glycoprotein advanced folding stages. Further,to determine if the GT-derived quality control is
operative with conformers displaying structures closely resembling those of native species and that,
therefore, no alternative ER retaining mechanisms are required when glycoproteins approach their
native folding, we generated and used as acceptor substrates neoglycoproteins bearing conformations
mimicking the very last-stage folding structures adopted by glycoproteins entering the ER lumen.
Results obtained demonstrate that GT is an exquisite sensor of glycoprotein conformations, able to
recognize folding intermediates only slightly differingfrom the native species. Finally, results obtained
using isolated subunits of a homotetrameric glycoprotein (soybean agglutinin) as acceptor substrate
showed that GT is also able to recognize hydrophobic interfaces exposed by properly folded
subunits not yet forming part of complete multimeric complexes, thus ensuring ER retention of
incompletely assembled multimeric species. The same mechanism operates, therefore, to monitor
glycoprotein acquisition of both tertiary and quaternary structures
Both the folding status of glycoprotein monomers and the assembly of multimeric glycoprotein
complexes are stringently controlled in the endoplasmic reticulum (ER) by a glucosyltransferase
(GT) that creates monoglucosylated structures recognized by ER-resident lectins (calnexin
and calreticulin). Monoglucosylated glycoproteinlectin interaction prevents exit to the Golgi of
structurally faulty macromolecules. Given that it only glucosylates incompletely assembled glycoprotein
multimers and glycoprotein monomers that do not display their native structures, GT serves as
a folding/assembly sensor. To explore the structural determinants for GT-mediated glucosylation, we
used as acceptor substrates a family of chemically glycosylated proteins derived from chymotrypsin
inhibitor 2. Structural characterization of species showing higher glucose acceptor capacity indicated
that GT recognizes solvent-accessible hydrophobic patches in molten globule-like conformers mimicking
glycoprotein advanced folding stages. Further,to determine if the GT-derived quality control is
operative with conformers displaying structures closely resembling those of native species and that,
therefore, no alternative ER retaining mechanisms are required when glycoproteins approach their
native folding, we generated and used as acceptor substrates neoglycoproteins bearing conformations
mimicking the very last-stage folding structures adopted by glycoproteins entering the ER lumen.
Results obtained demonstrate that GT is an exquisite sensor of glycoprotein conformations, able to
recognize folding intermediates only slightly differingfrom the native species. Finally, results obtained
using isolated subunits of a homotetrameric glycoprotein (soybean agglutinin) as acceptor substrate
showed that GT is also able to recognize hydrophobic interfaces exposed by properly folded
subunits not yet forming part of complete multimeric complexes, thus ensuring ER retention of
incompletely assembled multimeric species. The same mechanism operates, therefore, to monitor
glycoprotein acquisition of both tertiary and quaternary structures