Kim Junsoo, Lee Haemin, Roh Yeon Jin, Kim Han-Ul, Shin Donghyuk, Kim Sorah, Son Jonghyeon, Lee Aro, Kim Minseo, Park Junga, Hwang Seong Yun, Kim Kyunghwan, Lee Yong Kwon, Jung Hyun Suk, Hwang Kwang Yeon, Lee Byung Cheon
College of Life Sciences and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea.
Biochemistry Laboratory, Department of Biosystems and Biotechnology, Kangwon National University, 1 Kangwondaekak-gil, Chuncheon-si, Gangwon-do 24341, Republic of Korea.
IUCrJ. 2020 Jan 1;7(Pt 1):90-99. doi: 10.1107/S2052252519015409.
MICAL is an oxidoreductase that participates in cytoskeleton reorganization via actin disassembly in the presence of NADPH. Although three MICALs (MICAL1, MICAL2 and MICAL3) have been identified in mammals, only the structure of mouse MICAL1 has been reported. Here, the first crystal structure of human MICAL3, which contains the flavin-containing monooxygenase (FMO) and calponin-homology (CH) domains, is reported. MICAL3 has an FAD/NADP-binding Rossmann-fold domain for mono-oxygenase activity like MICAL1. The FMO and CH domains of both MICAL3 and MICAL1 are highly similar in structure, but superimposition of the two structures shows a different relative position of the CH domain in the asymmetric unit. Based on kinetic analyses, the catalytic efficiency of MICAL3 dramatically increased on adding F-actin only when the CH domain was available. However, this did not occur when two residues, Glu213 and Arg530, were mutated in the FMO and CH domains, respectively. Overall, MICAL3 is structurally highly similar to MICAL1, which suggests that they may adopt the same catalytic mechanism, but the difference in the relative position of the CH domain produces a difference in F-actin substrate specificity.
MICAL是一种氧化还原酶，在NADPH存在的情况下，通过肌动蛋白解聚参与细胞骨架重组。尽管在哺乳动物中已鉴定出三种MICAL（MICAL1、MICAL2和MICAL3），但仅报道了小鼠MICAL1的结构。在此，报道了人MICAL3的首个晶体结构，其包含含黄素单加氧酶（FMO）和卡波宁同源（CH）结构域。MICAL3具有一个用于单加氧酶活性的FAD/NADP结合罗斯曼折叠结构域，与MICAL1类似。MICAL3和MICAL1的FMO和CH结构域在结构上高度相似，但两种结构的叠加显示CH结构域在不对称单元中的相对位置不同。基于动力学分析，仅当CH结构域存在时，添加F-肌动蛋白会使MICAL3的催化效率显著提高。然而，当FMO和CH结构域中的两个残基分别为Glu213和Arg530突变时，情况并非如此。总体而言，MICAL3在结构上与MICAL1高度相似，这表明它们可能采用相同的催化机制，但CH结构域相对位置的差异导致了F-肌动蛋白底物特异性的差异。
