Internal-loops (also termed interior loops) in RNA are found where the double stranded RNA separates due to no Watson-Crick-Franklin base pairing between the nucleotides. Internal-loops differ from Stem-loops as they occur in middle of a stretch of double stranded RNA. The non-canonicoal residues result in the double helix becoming distorted due to unwinding, unstacking and kinking.
Internal-loops can be classified as either symmetrical or asymmetrical, with some asymmetrical internal-loops, also known as bulges. Many important structural motifs are composed of internal loops such as
the C-loop,
the docking-elbow,
kink-turns (k-turn),
the right-angle,
the sarcin/ricin loops (also called bulged-G motifs),
the twist-up motif
and the UAA/GAN internal loop motif.
Gallery of RNA motifs that host internal loops |
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A consensus secondary structure and primary sequence for the C-loop RNA motif.
A consensus secondary structure and primary sequence for the docking elbow RNA motif.
A consensus secondary structure and primary sequence for the kink-turn RNA motif.
A consensus secondary structure and primary sequence for the kink-turn RNA motif.
A consensus secondary structure and primary sequence for the right-angle RNA motif.
A consensus secondary structure and primary sequence for the 3` Sarcin-Ricin (or bulged-G) RNA motif.
A consensus secondary structure and primary sequence for the 5` Sarcin-Ricin (or bulged-G) RNA motif.
A consensus secondary structure and primary sequence for the twist-up RNA motif.
A consensus secondary structure and primary sequence for the UAA-GAN RNA motif.
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