Chemical Engineering Journal, 22 March, 2025, DOI：https://doi.org/10.1016/j.cej.2025.161854

Genetically encoded horse heart myoglobin for electron microscopy imaging in mammalian cells

Feng Zhang, Lianwan Chen, Jinfu Wen, Fahui Li, Guohua Song

Abstract

Electron microscopy (EM) offers high-resolution imaging of cellular ultrastructure, including membranes, organelles, and other nanoscale features. Current genetically encoded tags for catalyzing 3,3′-diaminobenzidine (DAB) polymerization, however, face limitations due to their bulky size, which often compromises the native localization of target proteins. To address this, we introduce a compact, genetically engineered variant of horse heart myoglobin (HM) as a novel DAB-polymerizing tag for labeling proteins in mammalian cells. Owing to its significantly smaller molecular weight, the HM fusion protein achieves superior localization accuracy compared to the widely used APEX2 system. Furthermore, HM exhibits exceptional resilience under stringent EM fixation protocols, maintaining both ultrastructural integrity and protein-specific labeling fidelity. These attributes position HM as a robust tool for high-resolution EM studies, uncovering the structure and physiological functions of key eukaryotic proteins.

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