Using Ancient Dynamin Segments to Understand Mitochondrial Endosymbiosis During the Statherian PaleoProtoerozoic

Ancient dynamin segments capture early stages of host–mitochondrial integration

Authors:

Purkanti et al

Abstract:

Eukaryotic cells use dynamins—mechano-chemical GTPases—to drive the division of endosymbiotic organelles. Here we probe early steps of mitochondrial and chloroplast endosymbiosis by tracing the evolution of dynamins. We develop a parsimony-based phylogenetic method for protein sequence reconstruction, with deep time resolution. Using this, we demonstrate that dynamins diversify through the punctuated transformation of sequence segments on the scale of secondary-structural elements. We find examples of segments that have remained essentially unchanged from the 1.8-billion-y-old last eukaryotic common ancestor to the present day. Stitching these together, we reconstruct three ancestral dynamins: The first is nearly identical to the ubiquitous mitochondrial division dynamins of extant eukaryotes, the second is partially preserved in the myxovirus-resistance-like dynamins of metazoans, and the third gives rise to the cytokinetic dynamins of amoebozoans and plants and to chloroplast division dynamins. The reconstructed sequences, combined with evolutionary models and published functional data, suggest that the ancestral mitochondrial division dynamin also mediated vesicle scission. This bifunctional protein duplicated into specialized mitochondrial and vesicle variants at least three independent times—in alveolates, green algae, and the ancestor of fungi and metazoans—accompanied by the loss of the ancient prokaryotic mitochondrial division protein FtsZ. Remarkably, many extant species that retain FtsZ also retain the predicted ancestral bifunctional dynamin. The mitochondrial division apparatus of such organisms, including amoebozoans, red algae, and stramenopiles, seems preserved in a near-primordial form.

Synthetic Bio Leaps and Bounds: Artificial Organelles Sweep Up Free Radicals

Researchers at the University of Basel have successfully developed artificial organelles that are able to support the reduction of toxic oxygen compounds. This opens up new ways in the development of novel drugs that can influence pathological states directly inside the cell. The results have been published in the Journal Nano Letters.

Free oxygen radicals are produced either as metabolic byproduct, or through environmental influences such as UV-rays and smog. Is the concentration of free radicals inside the organism elevated to the point where the antioxidant defense mechanism is overwhelmed, the result can be oxidative stress, which is associated with numerous diseases such as cancer of arthritis.

The aggressive molecules are normally controlled by endogenous antioxidants. Within this process, organelles located inside the cell, so-called peroxisomes, play an important part, since they assist in regulating the concentration of free oxygen radicals.

Paper link.