Biology subjects

Tran, L. T.

Publications and source records attributed to Tran, L. T..

4 recordsLinked to original sources

bioRxiv2025

Kinetic scheme of myosin phosphorylation by ZIP kinase

Zipper-interacting protein kinase (ZIPK) is a ubiquitous serine/threonine protein kinase that plays pivotal roles in regulating cell motility, division, and smooth muscle contractility through phosphorylation of myosin. In this study, we systematically investigated the phosphorylation reactions of smooth muscle myosin (SMM) by ZIPK. We found that ZIPK phosphorylates MRLC sequentially, first at Ser19 and then at Thr18, determined by quantitative mass spectrometry analysis on wild-type MRLC. Analysis on phosphomimic and unphosphorylatable MRLC mutants indicates that the phosphorylation rate at Ser19 on unphosphorylated MRLC is 1.5 times faster than that at Thr18 on Ser19-phosphorylated MRLC. Comparison between SMM and isolated MRLC revealed that the phosphorylation rate of SMM is slower than that of isolated MRLC. To dissect the molecular mechanism responsible for this difference, we measured interactions between ZIPK and SMM by co-sedimentation assay. The result suggests that the C-terminal domain of ZIPK interacts with the heavy chain of SMM, and as a result, competitive binding of ZIPK to MRLC and the myosin heavy chain suppresses phosphorylation of SMM compared to isolated MRLC. By incorporating the kinetic and dissociation constants obtained from mutant analysis and co-sedimentation assays, respectively, a simple kinetic model accurately reproduced the time courses of phosphorylation for both isolated MRLC and SMM. This provides systemic insight into the regulatory mechanism of myosin contractility by ZIPK.

biochemistry↗

bioRxiv2021

Structure and dynamics of Odinarchaeota tubulin and the implications for eukaryotic microtubule evolution

Tubulins are critical for the internal organization of eukaryotic cells, and understanding their emergence is an important question in eukaryogenesis. Asgard archaea are the closest known prokaryotic relatives to eukaryotes. Here, we elucidated the apo and nucleotide-bound X-ray structures of an Asgard tubulin from hydrothermal-living Odinarchaeota (OdinTubulin). The GTP-bound structure resembles a microtubule protofilament, with GTP bound between subunits, coordinating the "+" end subunit through a network of water molecules and unexpectedly by two cations. A water molecule is located suitable for GTP hydrolysis. Time course crystallography and electron microscopy revealed conformational changes on GTP hydrolysis. OdinTubulin forms tubules at high temperatures, with short curved protofilaments coiling around the tubule circumference, more similar to FtsZ, rather than running parallel to its length, as in microtubules. Thus, OdinTubulin represents an evolution intermediate between prokaryotic FtsZ and eukaryotic microtubule-forming tubulins.

evolutionary biology↗

bioRxiv2021

Plasmodium falciparum Calcium Dependent Protein Kinase 4 is critical for male gametogenesis and transmission to the mosquito vector

Gametocytes of the malaria parasite Plasmodium are taken up by the mosquito vector with an infectious blood meal, representing a critical stage for parasite transmission. Calcium dependent protein kinases (CDPKs) play key roles in calcium-mediated signaling across the complex life cycle of the parasite. We sought to understand their role in human parasite transmission from the host to the mosquito vector and thus investigated the role of the human-infective parasite Plasmodium falciparum CDPK4 in the parasite life cycle. P. falciparum cdpk4- parasites created by targeted gene deletion showed no effect in blood stage development or gametocyte development. However, cdpk4- parasites showed a severe defect in male gametogenesis and the emergence of flagellated male gametes. To understand the molecular underpinnings of this defect, we performed mass spectrometry-based phosphoproteomic analyses of wild type and Plasmodium falciparum cdpk4- late gametocyte stages, to identify key CDPK4-mediated phosphorylation events that may be important for the regulation of male gametogenesis. We further employed in vitro assays to identify these putative substrates of Plasmodium falciparum CDPK4. This indicated that CDPK4 regulates male gametogenesis by directly or indirectly controlling key essential events such as DNA replication, mRNA translation and cell motility. Taken together, our work demonstrates that PfCDPK4 is a central kinase that regulates exflagellation, and thereby is critical for parasite transmission to the mosquito vector. IMPORTANCETransmission of the malaria parasite to the mosquito vector is critical for the completion of the sexual stage of the parasite life cycle and is dependent on the release of male gametes from the gametocyte body inside the mosquito midgut. In the present study, we demonstrate that PfCDPK4 is critical for male gametogenesis and is involved in phosphorylation of proteins essential for male gamete emergence. Targeting PfCDPK4 and its substrates may provide insights into achieving effective malaria transmission-blocking strategies.

microbiology↗

bioRxiv2019

Complex eukaryotic-like actin regulation systems from Asgard archaea

Asgard archaea genomes contain potential eukaryotic-like genes that provide intriguing insight for the evolution of eukaryotes. The actin polymerization/depolymerization cycle is critical for providing force and structure for a variety of processes in eukaryotes, including membrane remodelling. Here, we identify actin filament severing, capping, annealing and bundling, and monomer sequestration activities by gelsolin proteins from Thorarchaeota (Thor), which complete a eukaryote-like actin depolymerization cycle. Thor gelsolins are comprised of one or two copies of the prototypical gelsolin domain and appear to be a record of an initial pre-eukaryotic gene duplication event, since eukaryotic gelsolins are generally comprised of three to six domains. X-ray crystal structure determination of these proteins in complex with mammalian actin revealed similar interactions to the first domain of human gelsolin. Asgard two-domain, but not one-domain, gelsolins contain calcium-binding sites, which is manifested in calcium-controlled activities. Expression of two-domain gelsolins in mammalian cells led to enhanced actin filament disassembly on ionomycin-triggered calcium release. This functional demonstration, at the cellular level, provides evidence for calcium-regulated actin cytoskeleton in Asgard archaea, and indicates that the calcium-regulated actin cytoskeleton predates eukaryotes. In eukaryotes, dynamic bundled filaments are responsible for shaping filopodia and microvilli. By correlation, the formation of the protrusions observed from Lokiarchaeota cell bodies may involve gelsolin-regulated actin structures.

evolutionary biology↗