Kazana, E. | Search bioRxiv

bioRxiv2020

Localization and Functional Characterization of the Alternative Oxidase in Naegleria

The Alternative oxidase (AOX) is a protein involved in maintaining the Krebs cycle in instances where the respiratory chain has been inhibited, while allowing for the maintenance of cell growth and necessary metabolic processes for survival. Among eukaryotes, alternative oxidases have disperse distribution and are found in plants, fungi and a few protists, including Naegleria ssp. Naegleria species are free-living unicellular amoeboflagellates, and include the pathogenic species of N. fowleri, the so-called brain eating amoeba. Using a multidisciplinary approach, we aimed to understand the evolution, localization and function of AOX and the role that plays in Naeglerias biology. Our analyses suggest that the protein was present in last common ancestor of the genus and structure prediction showed that all functional residues are also present in Naegleria species. Using a combination of cellular and biochemical techniques, we also functionally characterize N. gruberis AOX in its mitochondria and we demonstrate that its inactivation affects its proliferation. Consequently, we discuss the benefits of the presence of this protein in Naegleria species, along with its potential pathogenicity role in N. fowleri. We predict that our findings will spearhead new explorations to understand the cell biology, metabolism and evolution of Naegleria and other free-living relatives.

microbiology↗

bioRxiv2019

Hundreds of yeast mRNAs form a separately addressable, translation elongation-controlled regulon

In addition to the widespread and well documented control of protein synthesis by translation initiation, recent evidence suggests that translation elongation can also control protein synthesis rates. One of the proposed mechanisms leading to elongation control is the interference of slow ribosome movement around the start codon with efficient translation initiation. Here we estimate the frequency with which this mode of control occurs in bakers yeast growing in rich medium. Genome-wide data reveal that transcripts from around 20% of yeast genes show evidence of queueing ribosomes, which may be indicative of translation elongation control. Moreover, this subset of transcripts is sensitive to distinct regulatory signals compared to initiation-controlled mRNAs, and such distinct regulation occurs for example during the response to osmotic stress. Notethe previous version 2 of this preprint contained a Decision-Tree based analysis where we attempted to relate mRNA features to the presence or absence of queueing ribosome peaks. Since releasing that version, we performed additional controls for this analysis which strongly sugest that its results are random and should be ignored. Specifically, both the overall predictability and the importance of individual features is very similar for a real dataset where genes are labelled as containing a second SSU peak or not, and for a simulated control dataset containing an equal proportion of randomly labelled genes. We have removed this figure from the current version. The analysis together with the additional control remains accessible on the accompanying Github repository (github.com/tobiasvonderhaar/ribosomespeedcontrol) in the file "Figure 3 Obsolete (Classification).ipynb".

molecular biology↗