Arginine transport in Streptococcus lactis is catalyzed by a cationic exchanger.

Abstract

Streptococcus lactis metabolizes arginine via the arginine deiminase pathway to ornithine, C02, NH3, and ATP. The translocation of arginine and ornithine has been studied using membrane vesicles of galactose/arginine-grown cells of S. Iactis fused with cytochrome c oxidase proteoliposomes by the freeze/thaw-sonication procedure earlier described. In the presence of reduced cytochrome c the fused membranes rapidly accumulate ornithine. Addition of arginine releases accumulated ornithine. Rapid uncoupler-insensitive exchange between external arginine and internal ornithine is seen at rates that are at least 60-fold higher than the rate of protonmotive force-driven arginine translocation. This arginine:ornithine exchange activity was reconstituted in proteoliposomes after solubilization of S. lactis membranes with octyl 3D-glucopyranoside. These proteoliposomes catalyze a one-to-one exchange between arginine and ornithine. The arginine:ornithine exchange system is the first exchange system for cationic metabolites found in bacteria. Translocation of arginine via this system does not require metabolic energy obtained by arginine metabolism.Group N streptococci (e.g., Streptococcus lactis, Streptococcus cremoris, and Streptococcus lactis subsp. diacetylactis) are limited in their ability to ferment compounds other than sugars. An exception to this is arginine metabolism by S. lactis and S. lactis subsp. diacetylactis (1). This metabolism of arginine to ornithine, ammonia, and carbon dioxide via the arginine deiminase pathway (for review, see ref.2) is coupled to ATP synthesis, and ornithine is excreted (1).The arginine deiminase pathway includes three enzymes: (i) arginine deiminase (L-arginine transferase, EC 3.5.3.6) catalyzes the conversion of arginine into citrulline and ammonia, (ii) ornithine carbamoyltransferase (EC 2.1.3.3) catalyzes the phosphorolysis of citrulline, yielding ornithine and carbamoylphosphate, and (iii) carbamate kinase (ATP: carbamate phosphotransferase, EC 2.7.2.2) catalyzing the transfer of phosphate from carbamoylphosphate to ADP, yielding ATP, ammonia, and carbon dioxide. The properties of these enzymes have been described for S. lactis (1, 2). The physiology of arginine metabolism has been well characterized, but less information is available about the mechanism of arginine transport. High rates of arginine metabolism have been reported (1), suggesting that arginine is translocated into cells via a transport system with a large capacity. In this paper we describe a unique transport system for arginine in S. lactis. This transport system catalyzes a one-to-one exchange between arginine and ornithine. The arginine: ornithine antiporter can be extracted and reconstituted into proteoliposomes in a functional state.

Secondary solute transport in bacteria

“…Although alternative protocols have been devised [217,218], the basic method outlined above has been most successful for the reconstitution of several secondary transport proteins, i.e., the lactose transport protein (LacY), the melibiose transport protein (MelB), the arabinose transport protein (AraE), the proline carrier protein (PutP), the anion-linked antiporters (UhpT, GIpT, PgtP), and the galactose transport protein (GalP) of E. coli [188,210,214,215,219,220], the hexose phosphate/phosphate antiporter of L. lactis [221], the arginine/ornithine antiporter of L. lactis [84], the lactose transport protein (LacS) of S. thermophilus [89], the branched amino acid carriers of L. lactis [216] and P. aeruginosa [37], the alanine carrier proteins of thermophilic bacterium PS3 [222] and Nitrosomonas europaea [223], and the oxalate/formate antiporter (OxlT) of O. formigenes [224].…”

“…1-10) This class of antiport systems catalyzes the uptake of a solute (precursor, substrate) in a coupled exchange with another solute (product). The exchanged solutes can be anions such as sugar-phosphate/phosphate [81], oxalate/formate [82], malate/lactate [20,43], ATP/ ADP [83], or cations such as arginine/ornithine [84], agmatine/putrescine [85], putrescine/ornithine [86], or neutral solutes such as lactose/galactose [20]. In these exchange processes, in general, the substrate concentration gradient is directed inwards while the product concentration gradient is directed outwards.…”

Staphylococcus aureus Biofilm Metabolism and the Influence of Arginine on Polysaccharide Intercellular Adhesin Synthesis, Biofilm Formation, and Pathogenesis

“…The arc operon is comprised of genes for arginine deiminase (arcA), ornithine transcarbamylase (arcB), the arginine/ornithine antiporter (arcD), and carbamate kinase (arcC). The arginine/ ornithine antiporter is a cationic exchange system that catalyzes a one-to-one stoichiometric exchange of arginine and ornithine (12,16,42); hence, as the bacteria extract arginine from the culture medium, ornithine accumulates in the medium. As expected, inactivation of the arcD gene prevented the extraction of arginine from the culture medium and the accumulation of ornithine in the medium during biofilm growth (Fig.…”

arcD, the first gene of the arc operon for anaerobic arginine catabolism in Pseudomonas aeruginosa, encodes an arginine-ornithine exchanger

“…During anaerobic growth, arginine is stoichiometrically converted into ornithine (34), which is released into the growth medium. By analogy with the transport system of lactic acid bacteria (12) tococcus lactis catalyzes an electroneutral one-to-one exchange between arginine and ornithine and requires no additional metabolic energy (12,29).…”