Biology subjects

Meisinger, C.

Publications and source records attributed to Meisinger, C..

3 recordsLinked to original sources

bioRxiv2025

A Screening Approach Unveils an Unknown Mn2+ - dependent Endopolyphosphatase Activity in Yeast

Inorganic polyphosphate (polyP) is a ubiquitous biopolymer composed of multiple orthophosphates connected by energy-rich phosphoanhydride bonds. In organisms, polyP is digested by two types of enzymes: exopolyphosphatases, which shorten the chain from the ends by cleaving off monophosphate units, and endopolyphosphatases, which cut the chain internally. While several continuous methods are available to monitor exopolyphosphatase activity, endopolyphosphatase activity assays are less common and typically involve multiple tedious steps. Here, we introduce FRET-polyP8, a novel probe for real-time detection of endopolyphosphatase activity. The FRET assay enabled rapid, highly sensitive, single-step detection of specific endopolyphosphatase activity both from isolated proteins and cell extracts. The simple read-out additionally enabled enzyme inhibitor screening. Furthermore, a novel Mn2+-dependent endopolyphosphatase activity in bakers yeast was detected in a quadruple mutant, highlighting the ability to screen for metal-dependence of new endopolyphosphatase activity. This approach thus represents a significant addition to existing methodologies, facilitating the discovery and classification of new endopoly-phosphatases and their inhibitors to advance our understanding of polyP metabolism and regulation.

biochemistry↗

bioRxiv2018

Pptc7 is an essential phosphatase for promoting mammalian mitochondrial metabolism and biogenesis

Mitochondrial proteins are replete with phosphorylation; however, the origin, abundance, and functional relevance of these modifications are largely unclear. Nonetheless, mitochondria possess multiple resident phosphatases, suggesting that protein dephosphorylation may be broadly important for mitochondrial activities. To explore this, we deleted the poorly characterized matrix phosphatase Pptc7 from mice using CRISPR-Cas9 technology. Strikingly, Pptc7-/- mice exhibited marked hypoketotic hypoglycemia, elevated acylcarnitines, and lactic acidosis, and died soon after birth. Pptc7-/- tissues had significantly diminished mitochondrial size and protein content despite normal transcript levels, but consistently elevated phosphorylation on select mitochondrial proteins. These putative Pptc7 substrates include the protein translocase complex subunit Timm50, whose phosphorylation reduced import activity. We further find that phosphorylation in or near the mitochondrial targeting sequences of multiple proteins can disrupt their import rates and matrix processing. Overall, our data define Pptc7 as a protein phosphatase essential for proper mitochondrial function and biogenesis during the extrauterine transition.

biochemistry↗

bioRxiv2017

Biogenesis of a mitochondrial DNA inheritance machinery in the mitochondrial outer membrane

Mitochondria cannot form de novo but require mechanisms that mediate their inheritance to daughter cells. The parasitic protozoan Trypanosoma brucei has a single mitochondrion with a single-unit genome that is physically connected across the mitochondrial membranes to the basal body of the flagellum. This connection, termed tripartite attachment complex (TAC), is essential for the segregation of the replicated mitochondrial genomes prior to cytokinesis. Here we identify a protein complex consisting of three integral mitochondrial outer membrane proteins - TAC60, TAC42 and TAC40 - which are essential subunits of the TAC. TAC60 contains separable mitochondrial import and TAC-sorting signals and its biogenesis depends on the main outer membrane protein translocase. TAC40 is a member of the mitochondrial porin family, whereas TAC42 represents a novel class of mitochondrial outer membrane {beta}-barrel proteins. Consequently TAC40 and TAC42 contain C-terminal {beta}-signals. Thus in trypanosomes the highly conserved {beta}-barrel protein assembly machinery plays a major role in the biogenesis of its unique mitochondrial genome segregation system.

biochemistry↗