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首页> 外文期刊>Applied and Environmental Microbiology >Na+-Stimulated Transport of l-Methionine in Brevibacterium linens CNRZ 918
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Na+-Stimulated Transport of l-Methionine in Brevibacterium linens CNRZ 918

机译：Na +刺激短杆菌属CNRZ 918中L-蛋氨酸的转运

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The transport of l-methionine by the gram-positive species Brevibacterium linens CNRZ 918 is described. The one transport system (Km = 55 μM) found is constitutive for l-methionine, stereospecific, and pH and temperature dependent. Entry of l-methionine into cells is controlled by the internal methionine pool. Competition studies indicate that l-methionine and α-aminobutyric acid share a common carrier for their transport. Neither methionine derivatives substituted on the amino or carboxyl groups nor d-methionine was an inhibitor, whereas powerful inhibition was shown by l-cysteine, s-methyl-l-cysteine, dl-selenomethionine and dl-homocysteine. Sodium plays important and varied roles in l-methionine transport by B. linens CNRZ 918: (i) it stimulates transport without affecting the Km, (ii) it increases the specific activity (on a biomass basis) of the l-methionine transport system when present with methionine in the medium, suggesting a coinduction mechanism. l-Methionine transport requires an exogenous energy source, which may be succinic, lactic, acetic, or pyruvic acid but not glucose or sucrose. The fact that l-methionine transport was stimulated by potassium arsenate and to a lesser extent by potassium fluoride suggests that high-energy phosphorylated intermediates are not involved in the process. Monensin eliminates stimulation by sodium. Gramicidin and carbonyl cyanide-m-chlorophenylhydrazone act in the presence or absence of Na+. N-Ethylmaleimide, p-chloromercurobenzoate, valinomycin, sodium azide, and potassium cyanide have no or only a partial inhibitory effect. These results tend to indicate that the proton motive force reinforced by the Na+ gradient is involved in the mechanism of energy coupling of l-methionine transport by B. linens CNRZ 918. Thus, this transport is partially similar to the well-described systems in gram-negative bacteria, except for the role of sodium, which is very effective in B. linens, a species adapted to the high sodium levels of its niche.
机译：描述了革兰氏阳性亚麻杆菌CNRZ 918对1-蛋氨酸的转运。发现的一个转运系统（Lm = 55μM）对L-蛋氨酸具有组成型，立体定向性，且与pH和温度有关。 I-蛋氨酸进入细胞是由内部蛋氨酸池控制的。竞争研究表明，L-蛋氨酸和α-氨基丁酸具有共同的运输载体。氨基或羧基上取代的蛋氨酸衍生物和d-蛋氨酸都不是抑制剂，而l-半胱氨酸，s-甲基-1-半胱氨酸，dl-硒代蛋氨酸和dl-高半胱氨酸则没有抑制作用。钠在B.亚麻CNRZ 918的L-蛋氨酸运输中起着重要而多样的作用：（i）刺激运输而不影响Km，（ii）增加L-蛋氨酸运输系统的比活（以生物量为基础）当在培养基中与蛋氨酸一起存在时，表明存在共诱导机制。 1-甲硫氨酸转运需要外源能源，其可以是琥珀酸，乳酸，乙酸或丙酮酸，但不需要葡萄糖或蔗糖。甲硫氨酸钾刺激了甲硫氨酸的运输，而氟化钾刺激了甲硫氨酸的运输（在较小程度上），这一事实表明该过程不涉及高能磷酸化中间体。莫能菌素消除了钠的刺激。在存在或不存在Na +的情况下，豆蔻苷和羰基氰化物-间-氯苯基act起作用。 N-乙基马来酰亚胺，对氯mercurobenzoate，缬氨霉素，叠氮化钠和氰化钾没有或只有部分抑制作用。这些结果倾向于表明，Na +梯度增强的质子原动力参与了亚麻线虫CNRZ 918对L-蛋氨酸转运的能量耦合机理。因此，这种转运与以克为单位的众所周知的系统部分相似。 -负性细菌，除了钠的作用外，它在亚麻杆菌中非常有效，而亚麻杆菌适应于其生态位的高钠水平。

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