An ancient anion-binding structural module in RNA and DNA helicases

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• RNA and DNA helicases are crucial enzymes that unwind nucleic acid strands.
• These enzymes utilize a conserved structural motif for nucleic acid binding and translocation.
• Two principal superfamilies, SF1 and SF2, encompass the majority of known helicases.

Purpose of the Study:

• To analyze conserved structural features of SF1 and SF2 helicases.
• To elucidate the molecular interactions responsible for nucleic acid binding and translocation.
• To understand the structural basis for directional movement along DNA and RNA.

Main Methods:

• Analysis of available crystal structures of SF1 and SF2 helicases.
• Identification and comparison of conserved structural motifs and their interactions with nucleic acids.
• Mapping of common sequence motifs to structural locations.

Main Results:

• Identified conserved interactions between the phosphosugar backbone of trinucleotides and three strand-helix loops within a conserved structural module.
• Observed a conserved 'thr-motif' at the first and third loops, crucial for hydrogen bonding.
• Demonstrated structural congruence of these loops across helicase family members and tandem modules.

Conclusions:

• The conserved structural module and its interactions with the nucleic acid backbone are fundamental to helicase function.
• The thr-motif and other conserved interactions facilitate precise binding and directional translocation.
• Understanding these structural features provides insights into the mechanism of DNA and RNA helicases.