The Kink Turn, a Key Architectural Element in RNA Structure.

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Kink turns (k-turns) are prevalent RNA structural motifs.
• They introduce a significant axial bend (50°) into duplex RNA.
• K-turns are vital for tertiary interactions and binding proteins like the L7Ae family.

Purpose of the Study:

• To elucidate the structural basis of RNA kinking.
• To understand the factors influencing k-turn folding and conformational classes.
• To develop predictive rules for k-turn folding properties and structure based on sequence.

Main Methods:

• Analysis of standard k-turn structure, including bulge and base pairing.
• Investigation of minor groove association and cross-strand hydrogen bonds.
• Examination of conformational classes based on hydrogen bond receptors.
• Study of folding mechanisms, including the role of metal ions and sequence dependence.

Main Results:

• The standard k-turn involves a three-nucleotide bulge and G·A/A·G pairs.
• RNA kinking results from minor groove association stabilized by hydrogen bonds, primarily involving adenine bases.
• K-turns exhibit two conformational classes.
• Folding is influenced by sequence, with some k-turns folding in the presence of metal ions.

Conclusions:

• RNA sequence is a key determinant of k-turn folding properties and adopted structure.
• Predictive rules for k-turn folding and structure can be derived from local sequence information.
• Understanding k-turn structure-function relationships is crucial for RNA biology.