Yang H, Sasarman A, Inokuchi H, Adler J
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, 53706, USA.
Proc Natl Acad Sci U S A. 1996 Mar 19;93(6):2459-63. doi: 10.1073/pnas.93.6.2459.
Previously we showed that an Escherichia coli hemH mutant, defective in the ultimate step of heme synthesis, ferrochelatase, is somewhat better than 100-fold more sensitive than its wild-type parent in tumbling to blue light. Here we explore the effect of a hemG mutant, defective in the penultimate step, protoporphyrinogen oxidase. We found that a hemG mutant also is somewhat better than 100-fold more sensitive in tumbling to blue light compared to its wild-type parent. The amount of non-iron porphyrins accumulated in hemG or hemH mutants was more than 100-fold greater than in wild type. The nature of these accumulated porphyrins is described. When heme was present, as in the wild type, the non-iron (non-heme) porphyrins were maintained at a relatively low concentration and tumbling to blue light at an intensity effective for hemG or hemH did not occur. The function of tumbling to light is most likely to allow escape from the lethality of intense light.
此前我们发现，在血红素合成的最后一步存在缺陷的大肠杆菌hemH突变体，即亚铁螯合酶缺陷型，在对蓝光的翻滚反应中比其野生型亲本敏感100倍以上。在此我们探究了在倒数第二步存在缺陷的hemG突变体，即原卟啉原氧化酶缺陷型的影响。我们发现，与野生型亲本相比，hemG突变体在对蓝光的翻滚反应中也敏感100倍以上。hemG或hemH突变体中积累的非铁卟啉量比野生型中多100倍以上。描述了这些积累的卟啉的性质。当如野生型那样存在血红素时，非铁（非血红素）卟啉维持在相对较低的浓度，并且在对hemG或hemH有效的强度下不会发生对蓝光的翻滚反应。对光的翻滚反应的功能很可能是为了从强光的致死性中逃脱。
