Ellington W R, Roux K, Pineda A O
Department of Biological Science and Institute of Molecular Biophysics, Florida State University, Tallahassee 32306-4370, USA.
FEBS Lett. 1998 Mar 20;425(1):75-8. doi: 10.1016/s0014-5793(98)00204-x.
Mitochondrial creatine kinase (MiCK) occurs primarily as an octameric form localized in the mitochondrial intermembrane compartment in vertebrate tissues and echinoderm spermatozoa (both deuterostome groups). The octameric quaternary structure is thought to play important functional and enzyme targeting roles. We have found that the spermatozoa of the protostome polychaete Chaetopterus variopedatus contain three distinct isoenzymes of creatine kinase (CK) termed CK1, CK2 and CK3. CK3 appears to be present only in the sperm head/midpiece complex where mitochondria are restricted and has a subunit relative molecular mass (Mr) of 43.4 kDa. Gel permeation chromatography using Superdex 200HR showed that CK3 has a native Mr of 344.9 kDa indicating that this enzyme exists as an octamer. Electron micrographs of negatively stained CK3 preparations show structures which are virtually identical to those that have been seen for octameric vertebrate MiCK. The above observations show that CK3 from C. variopedatus displays great similarities to MiCKs from vertebrates and echinoderms. Octamerization of CK is not an advanced feature. The evolution of octameric subunit association is ancient and occurred prior to the divergence of protostomes and deuterostomes.
线粒体肌酸激酶（MiCK）主要以八聚体形式存在，定位于脊椎动物组织和棘皮动物精子（均为后口动物类群）的线粒体内膜间隙。八聚体四级结构被认为具有重要的功能和酶靶向作用。我们发现，原口动物多毛纲动物多变草苔虫的精子含有三种不同的肌酸激酶（CK）同工酶，分别称为CK1、CK2和CK3。CK3似乎仅存在于线粒体受限的精子头部/中段复合体中，其亚基相对分子质量（Mr）为43.4 kDa。使用Superdex 200HR进行的凝胶渗透色谱分析表明，CK3的天然Mr为344.9 kDa，这表明该酶以八聚体形式存在。CK3制备物的负染电子显微镜照片显示的结构与八聚体脊椎动物MiCK的结构几乎相同。上述观察结果表明，多变草苔虫的CK3与脊椎动物和棘皮动物的MiCK具有很大的相似性。CK的八聚化并非高级特征。八聚体亚基缔合的进化很古老，发生在原口动物和后口动物分化之前。
