Copper-Binding Properties and Structures of Methanobactins from Methylosinus trichosporium OB3b
Copper-Binding Properties and Structures of Methanobactins from Methylosinus trichosporium OB3b
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DOI：
10.1021/ic101965j
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发表时间：
2011-02-21
影响因子：
4.6
通讯作者：
Dennison, Christopher
中科院分区：
文献类型：
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作者：
El Ghazouani, Abdelnasser;Basle, Arnaud;Dennison, Christopher
甲烷氧化菌素（mbs）是由甲烷氧化菌产生的一类铜结合肽，与这些重要的环境微生物对铜的大量需求有关。唯一表征的mbs是来自发孢甲基弯菌OB 3b和甲基孢囊菌菌株SB 2的那些。M.丝孢霉OB 3b产生第二个mb（mb-Met），其缺失全长形式（FL-mb）的C-末端Met残基。分离的载铜的mbs结合Cu（I）。Met的缺失对Cu（I）位点的结构几乎没有影响，并且两种分子都介导了M中可溶性铁甲烷单加氧酶到颗粒状含铜酶的降解。发孢霉OB 3b细胞。在我们的实验条件下，在MBS的存在下，Cu（II）被还原，并且二硫化物在此过程中不起作用。这些分子的Cu（I）亲和性非常高，在pH >= 8.0时测定的值为（6-7）x 10（20）M-1。在pH 6.0时，对Cu（I）的亲和力低1个数量级。负载铜的FL-mb和mb-Met的还原电位分别为640和590 mV，突出了对Cu（I）的强烈偏好，并表明两种形式的不同Cu（II）亲和力。二硫键的断裂导致Cu（I）亲和力降低，在pH 7.5下降低至约9 x 10（18）M-1。这两种硫醇盐也可以结合Cu（I），尽管亲和力低得多（在pH 7.5时类似于3 × 10（15）M-1）。mbs对Cu（I）的高亲和力与铜吸收和保护中的生理作用一致。
Methanobactins (mbs) are a class of copper-binding peptides produced by aerobic methane oxidizing bacteria (methanotrophs) that have been linked to the substantial copper needs of these environmentally important microorganisms. The only characterized mbs are those from Methylosinus trichosporium OB3b and Methylocystis strain SB2. M. trichosporium OB3b produces a second mb (mb-Met), which is missing the C-terminal Met residue from the full-length form (FL-mb). The as-isolated copper-loaded mbs bind Cu(I). The absence of the Met has little influence on the structure of the Cu(I) site, and both molecules mediate switchover from the soluble iron methane monooxygenase to the particulate copper-containing enzyme in M. trichosporium OB3b cells. Cu(II) is reduced in the presence of the mbs under our experimental conditions, and the disulfide plays no role in this process. The Cu(I) affinities of these molecules are extremely high with values of (6-7) x 10(20) M-1 determined at pH >= 8.0. The affinity for Cu(I) is 1 order of magnitude lower at pH 6.0. The reduction potentials of copper-loaded FL-mb and mb-Met are 640 and 590 mV respectively, highlighting the strong preference for Cu(I) and indicating different Cu(II) affinities for the two forms. Cleavage of the disulfide bridge results in a decrease in the Cu(I) affinity to similar to 9 x 10(18) M-1 at pH 7.5. The two thiolates can also bind Cu(I), albeit with much lower affinity (similar to 3 x 10(15) M-1 at pH 7.5). The high affinity of mbs for Cu(I) is consistent with a physiological role in copper uptake and protection.