Membrane fission: model for intermediate structures

Prior research has shown that membrane budding-fission is essential for intracellular transport of proteins. Established knowledge includes the formation of coated buds connected to membranes via narrow necks. However, the mechanisms of fission itself remain unclear. No prior work had resolved the intermediate stages between budding and fission. This gap motivated the current theoretical analysis of the full pathway. The study addresses the transformation of the constricted neck into a hemifission intermediate. Understanding this transition could clarify how fission is driven by membrane stress. This paper contributes a model of the hemifission intermediate and its role in completing fission.

The aim of this study is to analyze the full pathway of membrane budding-fission. The specific problem is the lack of understanding about the intermediate stages between budding and fission. The researchers propose to model the transformation of the constricted membrane neck into a hemifission intermediate. They seek to explain how membrane stress drives this transformation. The motivation is to clarify the role of protein coats in fission. The study also aims to determine the energy and aperture size required for fission proteins. This work addresses a specific gap in the understanding of membrane fission. The findings may help explain how fission is completed after hemifission.

The researchers used theoretical modeling to analyze the budding-fission pathway. They considered two key intermediates: the constricted membrane neck and the hemifission intermediate. The model included the self-fusion of the inner monolayer of the neck. They calculated the membrane stress generated by the protein coat. The analysis focused on the energy required for fission proteins to act. The study compared hemifission with hemifusion to identify differences in curvature dependence. They formulated a 'job description' for fission proteins based on energy and aperture size. The theoretical framework was used to predict the spontaneous decay of the hemifission intermediate.

The strongest finding is that the hemifission intermediate forms when the inner monolayer fuses. The model shows that membrane stress from the protein coat drives the transformation of the constricted neck. The hemifission intermediate is distinct from hemifusion due to opposite curvature dependence. The study predicts that hemifission decays spontaneously into two membranes. The energy required for fission proteins to act is calculated based on the membrane stress. The aperture radius of the protein coat must reach a specific size to initiate fission. The model explains how fission is completed after hemifission. These results clarify the role of protein coats in membrane fission.

The authors propose that the hemifission intermediate is a crucial stage in membrane fission. They suggest that the transformation of the constricted neck is driven by membrane stress from the protein coat. The findings indicate that hemifission differs from hemifusion in curvature dependence. The study concludes that hemifission decays spontaneously into two membranes. The 'job description' for fission proteins includes energy delivery and aperture size. The model provides a framework for understanding how fission is completed. The conclusions are based on theoretical analysis of membrane stress and curvature. These findings may inform future studies on fission proteins and membrane dynamics.