Biology subjects

Tokmina-Lukaszewska, M.

Publications and source records attributed to Tokmina-Lukaszewska, M..

3 recordsLinked to original sources

bioRxiv2026

A Phosphorylation Switch Modulates Configurational Codes in the Oncofetal IGF2BP RNA Binding Paralogs

The insulin like growth factor 2 mRNA binding proteins (IGF2BP1-3) are oncofetal RNA regulators that control translation, stability, and localization of several transcripts, yet display paralog specific functions despite high structural similarity. Each paralog contains six RNA binding domains (two RRMs and four KH domains) linked by intrinsically disordered segments. mTORC2 phosphorylates IGF2BP1 and IGF2BP3 at a single conserved serine within the disordered linker between the RRM2 and KH1 domains, a modification required for proper regulation of mRNA translational fate. Pairing site specific phosphoserine incorporation with structural and biophysical interrogations, we show that this phosphorylation acts as a configurational switch that reorganizes long range arrangements of RNA binding domains and linkers without altering the secondary structure, and with only modest effects on RNA binding affinity. Critically, pSer driven rearrangements occur both in the RNA free state and upon RNA engagement, and the resulting architectures differ markedly between IGF2BP1 and IGF2BP3 despite >70% sequence identity. These paralog specific, phosphorylation dependent configurational landscapes likely underlie differences in mRNA recognition modes and functional outcomes. Our work identifies a post translational mechanism that tunes IGF2BP paralog dynamics across free and RNA bound states to program target mRNA selection, processing, and translational fate.

biochemistry↗

bioRxiv2025

Cryo-EM structure of a methanogen nitrogenase-PII protein supercomplex

Nitrogenases are metalloenzymes that catalyze the reduction of atmospheric dinitrogen to ammonia, sustaining the global nitrogen cycle. While bacterial nitrogenase has been extensively characterized, the architecture and regulation of archaeal nitrogenases remain unknown despite longstanding evidence of nitrogen fixation in methanogens. Here we report a 3.2 [A] cryo-electron microscopy structure of a native nitrogenase-PII protein supercomplex from Methanosarcina acetivorans. The structure reveals an unprecedented assembly of three NifDK heterotetramers bridged by six NifI1,2 heterotrimeric PII complexes, which sterically block NifH association and lock the enzyme in an inactive state. The PII complexes display asymmetric binding of ADP and 2-oxoglutarate, coupling nitrogenase inhibition directly to cellular energy and nitrogen status. Addition of 2-oxoglutarate and ATP releases the NifI complexes, stimulating a threefold increase in NifDK activity in vitro. This higher-order architecture uncovers a previously unrecognized regulatory strategy in methanogens, in which PII proteins drive nitrogenase oligomerization to control activity. The discovery that nitrogenase activity may be modulated through direct assembly into higher-order structures opens new avenues for exploring nitrogenase evolution, regulation, and biotechnological applications. One sentence summaryDiscovery of a nitrogenase-PII protein supercomplex in methanogens, uncovering a metabolite-gated assembly mechanism for nitrogenase inhibition.

biochemistry↗

bioRxiv2024

Cryo-EM captures the coordination of long-range allostery and asymmetric electron transfer by a bi-copper cluster in the nitrogenase-like DPOR complex

Enzymes that catalyze long-range electron transfer reactions are often structurally evolved to possess two symmetrical halves. The functional advantages and mechanistic principles for such architecture remain a mystery. Using Cryo-EM we capture snapshots of the nitrogenase-like Dark-operative Protochlorophyllide Oxidoreductase (DPOR) enzyme during substrate recognition and turnover. The structures reveal that asymmetry is enforced upon substrate binding and leads to an allosteric inhibition of protein-protein interactions and electron transfer in one half. Residues that form a conduit for electron transfer are aligned in one half while misaligned in the other. An ATP-turnover coupled switch is triggered once electron transfer is accomplished in one half and relayed through a bi-copper cluster at the oligomeric interface, leading to activation of enzymatic events in the other. The findings provide a mechanistic blueprint for regulation of asymmetric long-range electron transfer. One-Sentence SummaryA bi-copper cluster coordinates electron transfer for substrate reduction in the nitrogenase-like DPOR enzyme and the structures reveal how allostery and asymmetry are enacted over 100[A] and utilized for sequential electron transfer.

biochemistry↗