Effective ATPase activity and moderate chaperonin-cochaperonin interaction are important for the functional single-ring chaperonin system.
Escherichia coli chaperonin GroEL and its cochaperonin GroES are essential for cell growth as they assist folding of cellular proteins. The double-ring assembly of GroEL is required for the chaperone function, and a single-ring variant GroEL(SR) is inactive with GroES. Mutations in GroEL(SR) (A92T, D115N, E191G, and A399T) have been shown to render GroEL(SR)-GroES functional, but the molecular mechanism of activation is unclear. Here we examined various biochemical properties of these functional GroEL(SR)-GroES variants, including ATP hydrolysis rate, chaperonin-cochaperonin interaction, and in vitro protein folding activity. We found that, unlike the diminished ATPase activity of the inactive GroEL(SR)-GroES, all four single-ring variants hydrolyzed ATP at a level comparable to that of the double-ring GroEL-GroES. The chaperonin-cochaperonin interaction in these single-ring systems was weaker, by at least a 50-fold reduction, than the highly stable inactive GroEL(SR)-GroES. Strikingly, only GroEL(SR)D115N-GroES and GroEL(SR)A399T-GroES assisted folding of malate dehydrogenase (MDH), a commonly used folding substrate. These in vitro results are interesting considering that all four of the single-ring systems were able to substitute GroEL-GroES to support cell growth, suggesting that the precise action of chaperonin on MDH folding may not represent that on the intrinsic cellular substrates. Our findings that both effective ATP hydrolysis rate and moderate chaperonin-cochaperonin interaction are important factors for functional single-ring GroEL(SR)-GroES are reminiscent of the naturally occurring single-ring human mitochondrial chaperonin mtHsp60-mtHsp10. Differences in biochemical properties between the single- and double-ring chaperonin systems may be exploited in designing molecules for selective targeting.
Department of Molecular and Cellular Biochemistry, 212 S. Hawthorne Dr., Simon Hall 305B, Indiana University, Bloomington, IN 47405, USA.
Melissa
M
Illingworth
Department of Molecular and Cellular Biochemistry, 212 S. Hawthorne Dr., Simon Hall 305B, Indiana University, Bloomington, IN 47405, USA.
Jared
J
Salisbury
Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, China.
Wenqian
W
Li
Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, China.
Donghai
D
Lin
Department of Molecular and Cellular Biochemistry, 212 S. Hawthorne Dr., Simon Hall 305B, Indiana University, Bloomington, IN 47405, USA; Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, Fujian, China. Electronic address: linchen@indiana.edu.
Lingling
L
Chen
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D018835:Chaperonin 10 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018834:Chaperonin 60 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D008291:Malate Dehydrogenase / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D011487:Protein Conformation; D060066:Protein Interaction Maps; D058849:Protein Refolding
D018835:Chaperonin 10; D018834:Chaperonin 60; D029968:Escherichia coli Proteins; D008291:Malate Dehydrogenase; D000251:Adenosine Triphosphatases
ATPase activity; Chaperonin; Cochaperonin affinity; Single-ring GroEL–GroES; Substrate folding activity