Tomographic subvolume alignment and subvolume classification applied to myosin V and SIV envelope spikes

Area of Science:

• Structural biology
• Cellular imaging
• Biophysics

Background:

• Electron tomography (ET) combined with cryo-electron microscopy (cryo-EM) visualizes cellular structures near in vivo conditions.
• Limited angular tilt ranges in ET result in a
• missing wedge
• of missing data in reciprocal space, hindering analysis.
• Subvolume analysis in ET is crucial for characterizing macromolecular heterogeneity and interactions.

Purpose of the Study:

• To enhance subvolume processing protocols in electron tomography.
• To address the data gap caused by the
• missing wedge
• using novel reciprocal space methods.
• To assess the impact of the
• missing wedge
• on image classification and establish reliability limits.

Main Methods:

• Development of constrained correlation and weighted averaging in reciprocal space.
• Application of enhanced protocols to myosin V and simian immunodeficiency virus (SIV) envelope spikes.
• Model calculations using generated phantoms to investigate missing wedge effects.

Main Results:

• Successful application of new methods to analyze complex biological samples.
• Demonstration of improved subvolume analysis despite missing data.
• Quantification of the missing wedge's effect on image classification accuracy.

Conclusions:

• Enhanced reciprocal space processing effectively mitigates missing data issues in electron tomography.
• The developed methods improve the reliability and resolution of subvolume analysis for heterogeneous macromolecular assemblies.
• This work provides a framework for more accurate structural determination using cryo-ET data.