Orthogonal beta beta motifs in proteins

Area of Science:

• Structural Biology
• Protein Science
• Bioinformatics

Background:

• Protein structures are organized into hierarchical levels, including secondary structures like beta-strands.
• Super-secondary structures represent recurring arrangements of secondary structure elements.
• Understanding these motifs is crucial for deciphering protein function and evolution.

Purpose of the Study:

• To identify and characterize a specific super-secondary structural motif.
• To analyze the characteristics of the linking segments within this motif.
• To investigate the types of beta-turns present at the junction of the beta-strands.

Main Methods:

• Analysis of a dataset comprising 65 independent protein crystal structures.
• Identification of a super-secondary motif formed by two orthogonally oriented beta-strands.
• Examination of linking segments (≤5 residues) and conformational angles at the junction.

Main Results:

• A super-secondary structural motif of two orthogonally oriented beta-strands was identified in 42 examples from 14 proteins.
• The majority of these motifs feature a single amino acid residue as the linking element.
• Type VIII beta-turns were frequently observed at the connecting hinge, with Type II beta-turns also being common.

Conclusions:

• A distinct super-secondary structural motif, characterized by orthogonally oriented beta-strands and short linkers, is prevalent in proteins.
• The prevalence of single-residue linkers and specific beta-turn types (VIII and II) suggests structural and possibly functional significance.
• This finding contributes to the catalog of known protein structural motifs and their formation principles.