The group II intron ribonucleoprotein precursor is a large, loosely packed structure.
Group II self-splicing introns are phylogenetically diverse retroelements that are widely held to be the ancestors of spliceosomal introns and retrotransposons that insert into DNA. Folding of group II intron RNA is often guided by an intron-encoded protein to form a catalytically active ribonucleoprotein (RNP) complex that plays a key role in the activity of the intron. To date, possible structural differences between the intron RNP in its precursor and spliced forms remain unexplored. In this work, we have trapped the native Lactococcus lactis group II intron RNP complex in its precursor form, by deleting the adenosine nucleophile that initiates splicing. Sedimentation velocity, size-exclusion chromatography and cryo-electron microscopy provide the first glimpse of the intron RNP precursor as a large, loosely packed structure. The dimensions contrast with those of compact spliced introns, implying that the RNP undergoes a dramatic conformational change to achieve the catalytically active state.
Wadsworth Center, New York State Department of Health, Center for Medical Sciences, 150 New Scotland Avenue, Albany, NY 12201-2002, USA.
Tao
T
Huang
Tanvir R
TR
Shaikh
Kushol
K
Gupta
Lydia M
LM
Contreras-Martin
Robert A
RA
Grassucci
Gregory D
GD
Van Duyne
Joachim
J
Frank
Marlene
M
Belfort
D007438:Introns; D013294:Lactococcus lactis / Q000235:genetics; D008968:Molecular Conformation; D012322:RNA Precursors / Q000737:chemistry* / Q000302:isolation & purification; D016337:RNA, Catalytic / Q000737:chemistry* / Q000302:isolation & purification; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure
D012322:RNA Precursors; D016337:RNA, Catalytic; D012261:Ribonucleoproteins