Biology subjects

Hunte, C.

Publications and source records attributed to Hunte, C..

2 recordsLinked to original sources

bioRxiv2022

Conformational dynamics and target-dependent myristoyl switch of calcineurin B homologous protein 3

Calcineurin B homologous protein 3 (CHP3) is an EF-hand Ca2+-binding protein involved in regulation of cancerogenesis, cardiac hypertrophy and neuronal development via interactions with sodium/proton exchangers (NHEs) and signalling proteins. CHP3 binds Ca2+ with micromolar affinity providing the basis to respond to intracellular Ca2+ signals. Ca2+ binding and myristoylation are important for CHP3 function but the underlying molecular mechanism remained elusive. Here, we show that Ca2+ binding and myristoylation independently affect conformational dynamics and functions of human CHP3. Ca2+ binding increased flexibility and hydrophobicity of CHP3 indicative of an open conformation. CHP3 in open Ca2+-bound conformation had higher affinity for NHE1 and associated stronger with lipid membranes compared to the closed Mg2+-bound conformation. Myristoylation enhanced flexibility of CHP3 and decreased its affinity to NHE1 independently of the bound ion, but did not affect its binding to lipid membranes. The data exclude the proposed Ca2+-myristoyl switch for CHP3. Instead, they document a Ca2+-independent exposure of the myristoyl moiety induced by binding of the target peptide to CHP3 enhancing its association to lipid membranes. We name this novel regulatory mechanism "target-dependent myristoyl switch". Taken together, the interplay of Ca2+ binding, myristoylation and target binding allows for a context-specific regulation of CHP3 functions.

biochemistry↗

bioRxiv2022

Remorin proteins serve as membrane topology scaffolds in plants

Organization of membrane topologies in plants has so far been mainly attributed to the cell wall and the cytoskeleton. Taking rhizobial infections of legume root cells, where plasma membranes undergo dynamic and large-scale topology changes, as an initial model, we challenged this paradigm and tested whether additional scaffolds such as plant-specific remorins that accumulate on highly curved and often wall-less plasma membrane domains, control local membrane dynamics. Indeed, loss-of-function mutants of the remorin protein SYMREM1 failed to develop stabilized membrane tubes as found in colonized cells in wild-type plants, but released empty membrane spheres instead. Expression of this and other remorins in wall-less protoplasts allowed engineering different membrane topologies ranging from membrane blebs to long membrane tubes. Reciprocally, mechanically induced membrane indentations were equally stabilized by SYMREM1. This function is likely supported by remorin oligomerization into antiparallel dimers and the formation of higher order membrane scaffolding structures. Taken together we describe an evolutionary confined mechanism that allows the stabilization of large-scale membrane conformations and curvatures in plants. One-sentence summaryThe remorin SYMREM1 evolved as structural membrane scaffold that stabilizes membrane tubulation and curvature during symbiotic intracellular infections.

plant biology↗