Folding of malate dehydrogenase inside the GroEL-GroES cavity.
The chaperonin GroEL binds nonnative substrate protein in the hydrophobic central cavity of an open ring. ATP and GroES binding to the same ring converts this cavity into an encapsulated, hydrophilic chamber that mediates productive folding. A 'rack' mechanism of initial protein unfolding proposes that, upon GroES and ATP binding, the polypeptide is stretched between the binding sites on the twisting apical domains of GroEL before complete release into the chamber. Here, the structure of malate dehydrogenase (MDH) subunit during folding is monitored by deuterium exchange, peptic fragment production and mass spectrometry. When bound to GroEL, MDH exhibits a core of partially protected secondary structure that is only modestly deprotected upon ATP and GroES binding. Moreover, deprotection is broadly distributed throughout MDH, suggesting that it results from breaking hydrogen bonds between MDH and the cavity wall or global destabilization, as opposed to forced mechanical unfolding.
Chen
J
J
Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, USA.
Walter
S
S
Horwich
A L
AL
Smith
D L
DL
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D018835:Chaperonin 10 / Q000378:metabolism*; D018834:Chaperonin 60 / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003903:Deuterium / Q000378:metabolism; D019281:Dimerization; D006860:Hydrogen Bonding; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000737:chemistry* / Q000378:metabolism*; D013058:Mass Spectrometry; D008929:Mitochondria, Heart; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D013552:Swine
D018835:Chaperonin 10; D018834:Chaperonin 60; D010446:Peptide Fragments; D021122:Protein Subunits; D000255:Adenosine Triphosphate; D003903:Deuterium; D008291:Malate Dehydrogenase