Perturbed ATPase activity and not "close confinement" of substrate in the cis cavity affects rates of folding by tail-multiplied GroEL

@article{citeulike:1299820, abstract = {Folding of substrate proteins inside the sequestered and hydrophilic GroEL-GroES cis cavity favors production of the native state. Recent studies of GroEL molecules containing volume-occupying multiplications of the flexible C-terminal tail segments have been interpreted to indicate that close confinement of substrate proteins in the cavity optimizes the rate of folding: the rate of folding of a larger protein, Rubisco (51 kDa), was compromised by multiplication, whereas that of a smaller protein, rhodanese (33 kDa), was increased by tail duplication. Here, we report that this latter effect does not extend to the subunit of malate dehydrogenase (MDH), also 33 kDa. In addition, single-ring versions of tail-duplicated and triplicated molecules, comprising stable cis complexes, did not produce any acceleration of folding of rhodanese or MDH, nor did they show significant retardation of the folding of Rubisco. Tail quadruplication produced major reduction in recovery of native protein with both systems, the result of strongly reduced binding of all three substrates. When steady-state ATPase of the tail-multiplied double-ring GroELs was examined, it scaled directly with the number of tail segments, with more than double the normal ATPase rate upon tail triplication. As previously observed, disturbance of ATPase activity of the cycling double-ring system, and thus of "dwell time" for the folding protein in the cis cavity, produces effects on folding rates. We conclude that, within the limits of the {approx}10\% decrease of cavity volume produced by tail triplication, there does not appear to be an effect of "close confinement" on folding in the cis cavity. 10.1073/pnas.0700820104}, author = {Farr, George W. and Fenton, Wayne A. and Horwich, Arthur L. }, citeulike-article-id = {1299820}, comment = {cf. Tang et al.(2006) Cell-125\_903}, journal = {PNAS}, keywords = {chaperonin, confinement, experiment, groel}, month = {March}, number = {13}, pages = {5342--5347}, posted-at = {2007-05-16 11:52:11}, priority = {2}, title = {Perturbed ATPase activity and not "close confinement" of substrate in the cis cavity affects rates of folding by tail-multiplied GroEL}, url = {http://www.pnas.org/cgi/content/abstract/104/13/5342}, volume = {104}, year = {2007} }

TY - JOUR ID - citeulike:1299820 L3 - citeulike-article-id:1299820 TI - Perturbed ATPase activity and not "close confinement" of substrate in the cis cavity affects rates of folding by tail-multiplied GroEL JF - PNAS VL - 104 IS - 13 SP - 5342 EP - 5347 N2 - Folding of substrate proteins inside the sequestered and hydrophilic GroEL-GroES cis cavity favors production of the native state. Recent studies of GroEL molecules containing volume-occupying multiplications of the flexible C-terminal tail segments have been interpreted to indicate that close confinement of substrate proteins in the cavity optimizes the rate of folding: the rate of folding of a larger protein, Rubisco (51 kDa), was compromised by multiplication, whereas that of a smaller protein, rhodanese (33 kDa), was increased by tail duplication. Here, we report that this latter effect does not extend to the subunit of malate dehydrogenase (MDH), also 33 kDa. In addition, single-ring versions of tail-duplicated and triplicated molecules, comprising stable cis complexes, did not produce any acceleration of folding of rhodanese or MDH, nor did they show significant retardation of the folding of Rubisco. Tail quadruplication produced major reduction in recovery of native protein with both systems, the result of strongly reduced binding of all three substrates. When steady-state ATPase of the tail-multiplied double-ring GroELs was examined, it scaled directly with the number of tail segments, with more than double the normal ATPase rate upon tail triplication. As previously observed, disturbance of ATPase activity of the cycling double-ring system, and thus of "dwell time" for the folding protein in the cis cavity, produces effects on folding rates. We conclude that, within the limits of the {approx}10% decrease of cavity volume produced by tail triplication, there does not appear to be an effect of "close confinement" on folding in the cis cavity. 10.1073/pnas.0700820104 KW - chaperonin KW - confinement KW - experiment KW - groel N1 - cf. Tang et al.(2006) Cell-125_903 AU - Farr, George AU - Fenton, Wayne AU - Horwich, Arthur PY - 2007/03/27/ UR - http://www.pnas.org/cgi/content/abstract/104/13/5342 ER -