Conformational rearrangements of an archaeal chaperonin upon ATPase cycling.
Curr Biol
; 10(7): 405-8, 2000 Apr 06.
Article
en En
| MEDLINE
| ID: mdl-10753750
Chaperonins are double-ring protein assemblies with a central cavity that provides a sequestered environment for in vivo protein folding. Their reaction cycle is thought to consist of a nucleotide-regulated alternation between an open substrate-acceptor state and a closed folding-active state. The cavity of ATP-charged group I chaperonins, typified by Escherichia coli GroEL [1], is sealed off by a co-chaperonin, whereas group II chaperonins--the archaeal thermosome and eukaryotic TRiC/CCT [2]--possess a built-in lid [3-5]. The mechanism of the lid's rearrangements requires clarification, as even in the absence of nucleotides, thermosomes of Thermoplama acidophilum appear open in vitrified ice [6] and closed in crystals [4]. Here we analyze the conformation of the thermosome at each step of the ATPase cycle by small-angle neutron scattering. The apo-chaperonin is open in solution, and ATP binding induces its further expansion. Closure seems to occur during ATP hydrolysis and before phosphate release, and represents the rate-limiting step of the cycle. The same closure can be triggered by the crystallization buffer. Thus, the allosteric regulation of group II chaperonins appears different from that of their group I counterparts.
Buscar en Google
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Adenosina Trifosfatasas
/
Chaperoninas
/
Proteínas Arqueales
Idioma:
En
Revista:
Curr Biol
Asunto de la revista:
BIOLOGIA
Año:
2000
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Reino Unido