title: Metal binding and base ionization in the U6 RNA intramolecular stem-loop structure.
abstract: U6 RNA is a key component of the catalytic core of the spliceosome. A metal ion essential for the first catalytic step of pre-mRNA splicing binds to the U80 Sp phosphate oxygen within the yeast U6 intramolecular stem-loop (ISL). Here we present the first structural data for U6 RNA, revealing the three-dimensional structure of the highly conserved U6 ISL. The ISL binds metal ion at the U80 site with the same stereo specificity as the intact spliceosome. The metal-binding site is adjacent to a readily protonated C.A wobble pair. Protonation of the C.A pair and metal binding are mutually antagonistic. These results support a ribozyme model for U6 RNA function and suggest a possible mechanism for the regulation of RNA splicing.
authors: Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, Wisconsin 53706, USA.
authors: Anna
authors: A
authors: Huppler
authors: Laura J
authors: LJ
authors: Nikstad
authors: Anne M
authors: AM
authors: Allmann
authors: David A
authors: DA
authors: Brow
authors: Samuel E
authors: SE
authors: Butcher
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D019143:Evolution, Molecular; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008670:Metals / Q000378:metabolism*; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D009690:Nucleic Acid Conformation; D011522:Protons; D012326:RNA Splicing; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D007477:Ions; D008670:Metals; D011522:Protons; D012331:RNA, Fungal; D012342:RNA, Small Nuclear; C405486:U6 small nuclear RNA