Beyond BLASTing: tertiary and quaternary structure analysis helps identify major vault proteins

Area of Science:

• Structural biology
• Bioinformatics
• Computational biology

Background:

• Protein sequence similarity alone is insufficient for determining functional homology.
• The major vault protein (MVP) forms essential barrel-like vault particles through oligomerization.
• Understanding MVP structure and function is crucial across eukaryotic organisms.

Purpose of the Study:

• To develop and validate a computational method for predicting protein homology using 3D structure and quaternary structure analysis.
• To evaluate the potential for homologous sequences to form functional quaternary structures.
• To identify novel MVP homologs in understudied organisms.

Main Methods:

• Utilized I-TASSER for protein 3D structure prediction of putative MVP sequences.
• Employed RosettaDock to analyze predicted structures for quaternary association potential.
• Validated the method using experimentally determined structures and negative controls (randomized sequences).

Main Results:

• The method accurately predicted known MVP structures and identified homologous sequences capable of forming quaternary structures.
• Positive controls (rat and sea urchin MVP) and kinetoplast homologs were correctly identified and predicted to oligomerize.
• A randomized rat MVP sequence failed to predict an MVP-like structure, validating the method's specificity.

Conclusions:

• Combining 3D structure prediction with docking analysis enhances the assessment of protein homology.
• The developed protocol can reliably predict the quaternary structure formation potential of MVP sequences.
• Six putative homologous MVP sequences were identified in Naegleria gruberi, including two predicted to be structurally similar to rat MVP despite significant length differences.