Biology subjects

Lechno-Yossef, S.

Publications and source records attributed to Lechno-Yossef, S..

3 recordsLinked to original sources

bioRxiv2026

A novel class of conserved sucrose-phosphate phosphatases highlights the diversity of cyanobacterial sucrose metabolism

Sucrose metabolism is an important feature of the physiology of the green lineage of photosynthetic organisms and has therefore been the subject of considerable research on plants, algae, and cyanobacteria. Canonical sucrose biosynthesis pathways often involve the condensation of NDP-glucose and fructose-6-phosphate through the action of sucrose-phosphate synthase, then the dephosphorylation of sucrose 6-phosphate into sucrose via sucrose-phosphate phosphatase (SPP). However, many cyanobacterial genomes encode multiple homologs of SPP proteins (SPP-like), including variants that appear to lack key residues reported to be important for sucrose 6-phosphate binding. Herein, we examine these SPP-like proteins, focusing on the biochemical and physiological characterization of the SPP-like protein encoded by the cyanobacterial model, Synechococcus elongatus PCC 7942. Bioinformatic analysis suggests that the SPP-like family of proteins is highly conserved across cyanobacterial species and forms distinct phylogenetic clades that are more widely distributed than the canonical SPP proteins themselves. Biochemical analysis of the purified S. elongatus PCC 7942 SPP-like protein reveals that it not only retains the capacity to dephosphorylate sucrose 6-phosphate, but it also may have physiologically relevant phosphatase activity on 3-phosphoglycerate (3-PGA). We provide evidence that the SPP-like family of proteins represents a well-conserved group of phosphatases across cyanobacteria and suggest some enzymes in this family may have evolved a broader substrate specificity relative to the well-characterized SPP family. Our results have broader implications for cyanobacterial regulation of sucrose biosynthesis and other key steps of central carbon metabolism.

biochemistry↗

bioRxiv2023

The phycobilisome linker protein ApcG interacts with photosystem II and regulates energy transfer to photosystem I in Synechocystis sp. PCC 6803

Photosynthetic organisms harvest light using pigment-protein super-complexes. In cyanobacteria, these are water-soluble antennae known as phycobilisomes (PBSs). The light absorbed by PBS is transferred to the photosystems in the thylakoid membrane to drive photosynthesis. The energy transfer between these super-complexes implies that protein-protein interactions allow the association of PBS with the photosystems. However, the specific proteins involved in the interaction of PBS with the photosystems are not fully characterized. Here, we show that the newly discovered PBS linker protein ApcG interacts specifically with photosystem II through its N-terminal region. Growth of cyanobacteria is impaired in apcG deletion strains under light-limiting conditions. Furthermore, complementation of these strains using a phospho-mimicking version of ApcG exhibit reduced growth under normal growth conditions. Interestingly, the interaction of ApcG with photosystem II is affected when a phospho-mimicking version of ApcG is used, targeting the positively charged residues interacting with thylakoid membrane suggesting a regulatory role mediated by phosphorylation of ApcG. Low temperature fluorescence measurements showed increased photosystem I fluorescence in apcG deletion and complementation strains. The photosystem I fluorescence was the highest in the phospho-mimicking complementation strain while pull-down experiment showed no interaction of ApcG with PSI under any tested condition. Our results highlight the importance of ApcG for selectively directing energy harvested by the PBS and implies that the phosphorylation status of ApcG plays a role in regulating energy transfer from PSII to PSI.

plant biology↗

bioRxiv2017

Synthetic OCP Heterodimers are Photoactive and Recapitulate the Fusion of Two Primitive Carotenoproteins in the Evolution of Cyanobacterial Photoprotection

The Orange Carotenoid Protein (OCP) governs photoprotection in the majority of cyanobacteria. It is structurally and functionally modular, comprised of a C-terminal regulatory domain (CTD), an N-terminal effector domain (NTD) and a ketocarotenoid; the chromophore spans the two domains in the ground state and translocates fully into the NTD upon illumination. Using both the canonical OCP1 and the presumably more primitive OCP2 from Fremyella diplosiphon, we show that an NTD-CTD heterodimer forms when the domains are expressed as separate polypeptides. The carotenoid is required for the heterodimeric association, assembling an orange complex which is stable in the dark. Both OCP1 and OCP2 heterodimers are photoactive, undergoing light-driven heterodimer dissociation, but differ in their ability to reassociate in darkness, setting the stage for bioengineering photoprotection in cyanobacteria as well as for developing new photoswitches for biotechnology. Additionally, we reveal that homodimeric CTD can bind carotenoid in the absence of NTD, and name this truncated variant the C-terminal domain-like Carotenoid Protein (CCP). This finding supports the hypothesis that the OCP evolved from an ancient fusion event between genes for two different carotenoid-binding proteins ancestral to the NTD and CTD. We suggest that the CCP and its homologs constitute a new family of carotenoproteins within the NTF2-like superfamily found across all kingdoms of life.

plant biology↗