Characteristics of the glmS ribozyme suggest only structural roles for divalent metal ions.
The glmS ribozyme is a riboswitch class that occurs in certain Gram-positive bacteria, where it resides within mRNAs encoding glucosamine 6-phosphate synthase. Members of this self-cleaving ribozyme class rapidly catalyze RNA transesterification upon binding GlcN6P, and genetic evidence suggests that this cleavage event is important for down-regulating GlmS protein expression. In this report, we present a refined secondary structure model of the glmS ribozyme and determine the importance of a conserved pseudoknot structure for optimal ribozyme function. Analyses of deletion constructs demonstrate that the pseudoknot, together with other structural elements, permits the ribozyme to achieve maximum rate constants for RNA cleavage at physiologically relevant Mg2+ concentrations. In addition, we show that substantial rate enhancements are supported by an exchange-inert cobalt (III) complex and by molar concentrations of monovalent ions. Our findings indicate that the glmS ribozyme forms a complex structure to employ catalytic strategies that do not require the direct participation of divalent metal ions.
Roth
Adam
A
Howard Hughes Medical Institute, Department of Molecular, Cellular and Developmental Biology, Yale University, P. O. Box 208103, New Haven, Connecticut 06520-8103, USA.
Nahvi
Ali
A
Lee
Mark
M
Jona
Inbal
I
Breaker
Ronald R
RR
D001409:Bacillus cereus / Q000201:enzymology / Q000235:genetics; D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002413:Cations, Divalent; D007700:Kinetics; D008670:Metals / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing)
D001426:Bacterial Proteins; D002413:Cations, Divalent; D008670:Metals; D012329:RNA, Bacterial; C000731191:component S, glutamate mutase protein, Bacteria; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing)