Moody A J, Cooper C E, Gennis R B, Rumbley J N, Rich P R
Glynn Research Institute, Bodmin, Cornwall, U.K.
Biochemistry. 1995 May 23;34(20):6838-46. doi: 10.1021/bi00020a030.
The fully oxidized fast form of cytochrome bo from Escherichia coli is shown to convert spontaneously to a slow form when stored at -20 degrees C in 50 mM potassium borate, pH 8.5, containing 0.5 mM potassium EDTA. Evidence for the conversion, and that the form produced is analogous to the slow form of bovine heart cytochrome c oxidase, comes from (a) decreases in the extents of fast (k = 1-2 x 10(3) M-1 s-1) H2O2 binding and fast (k = 20-30 M-1 s-1) cyanide binding; (b) changes in the optical spectrum that are like those induced by formate, i.e., a blue shift in the Soret absorption band, loss of absorbance in the alpha and beta bands, and a red shift in the "630 nm" charge-transfer band; (c) changes in the EPR spectrum that are like those induced by formate, i.e., disappearance of signals at g = 8.6 and g = 3.71, and appearance of signals at g approximately 13, g = 3.14, and g = 2.58; and (d) appearance of a slow phase of reduction of heme o by dithionite. The mutant enzyme E286Q also converts to a slow form under the same conditions, as shown by (a) a decrease in the extent of fast H2O2 binding; (b) changes in the optical spectrum like those seen with wild-type enzyme; and (c) changes in the EPR spectrum that are like those induced by formate, i.e., disappearance of signals at g = 7.3 and g = 3.6 and appearance of signals at g approximately 13, g = 3.18, and g = 2.59.(ABSTRACT TRUNCATED AT 250 WORDS)
已证明，来自大肠杆菌的细胞色素bo的完全氧化快速形式，在-20℃下于含有0.5 mM 乙二胺四乙酸钾的50 mM硼酸钾（pH 8.5）中储存时会自发转化为慢速形式。这种转化的证据以及所产生的形式类似于牛心脏细胞色素c氧化酶的慢速形式，来自于：(a) 快速（k = 1 - 2×10³ M⁻¹ s⁻¹）H₂O₂结合程度和快速（k = 20 - 30 M⁻¹ s⁻¹）氰化物结合程度降低；(b) 光谱变化类似于甲酸盐诱导的变化，即Soret吸收带蓝移、α和β带吸光度丧失以及“630 nm”电荷转移带红移；(c) EPR光谱变化类似于甲酸盐诱导的变化，即g = 8.6和g = 3.71处信号消失，g约为13、g = 3.14和g = 2.58处信号出现；以及(d) 连二亚硫酸盐还原血红素o出现慢速阶段。突变酶E286Q在相同条件下也会转化为慢速形式，表现为：(a) 快速H₂O₂结合程度降低；(b) 光谱变化与野生型酶相似；以及(c) EPR光谱变化类似于甲酸盐诱导的变化，即g = 7.3和g = 3.6处信号消失，g约为13、g = 3.18和g = 2.59处信号出现。（摘要截短于250字）
