Sulfur Mobilization in Cyanobacteria

Abstract

Sulfur mobilization represents one of the key steps in ubiquitous Fe-S clusters assembly and is performed by a recently characterized set of proteins encompassing cysteine desulfurases, assembly factors, and shuttle proteins. Despite the evolutionary conservation of these proteins, some degree of variability among organisms was observed, which might reflect functional specialization. L-Cyst(e)ine lyase (C-DES), a pyridoxal 5-phosphatedependent enzyme identified in the cyanobacterium Synechocystis, was reported to use preferentially cystine over cysteine with production of cysteine persulfide, pyruvate, and ammonia. In this study, we demonstrate that C-DES sequences are present in all cyanobacterial genomes and constitute a new family of sulfur-mobilizing enzymes, distinct from cysteine desulfurases. The functional properties of C-DES from Synechocystis sp. PCC 6714 were investigated under pre-steady-state and steady-state conditions. Single wavelength and rapid scanning stopped-flow kinetic data indicate that the internal aldimine reacts with cystine forming an external aldimine that rapidly decays to a transient quinonoid species and stable tautomers of the ␣-aminoacrylate Schiff base. In the presence of cysteine, the transient formation of a dipolar species precedes the selective and stable accumulation of the enolimine tautomer of the external aldimine, with no formation of the ␣-aminoacrylate Schiff base under reducing conditions. Effective sulfur mobilization from cystine might represent a mechanism that allows adaptation of cyanobacteria to different environmental conditions and to light-dark cycles.

Emerging ground and excited state dipole moments and external electric field effect on electronic structure. A solvatochromism and theoretical study on 2-((phenylimino)methyl)phenol derivatives

“…Schiff bases have wide applications in medicine, pharmaceutical, industrial, chemosensor chemistry and biological processes [1][2][3][4][5][6][7]. Proton tautomerism plays a significant role in various fields of chemistry and biochemistry [8].…”

Biochemical Discrimination between Selenium and Sulfur 2: Mechanistic Investigation of the Selenium Specificity of Human Selenocysteine Lyase

“…2A and 2B), make the substrate gem-diamine species (Fig. 1) the most likely explanation for this absorbance [17], [18], [19], [24], [29], [30]. Based on the general reaction scheme, the rapidly forming 420 nm absorbing species in both systems (Fig.…”

“…1), with some studies suggesting a variant of the mechanism in that the SH or Se − is eliminated directly from the Sec/Cys quinonoid intermediate (red dotted arrows in Fig. 1) [10], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24].…”

Zinc and Cadmium Complexes of a Plant Metallothionein under Radical Stress: Desulfurisation Reactions Associated with the Formation of trans‐Lipids in Model Membranes

“…[52] Other interesting relations can be found in the change in redox potential [53] and in the mechanisms of mobilization of sulfur that are adaptation processes linked to their reactivity. [54] Experimental Section Preparation and characterisation of recombinant M II -QsMT aggregates (M II = Zn II or Cd II ): QsMT was obtained in its Zn-, or Cd-complexed forms by heterologous synthesis in E. coli, followed by purification by affinity chromatography and fast protein liquid chromatography (FPLC). The clone containing the pGEX-QsMT plasmid was previously constructed as reported.…”