Crystal structure of the MecA degradation tag.
MecA is an adaptor protein that regulates the assembly and activity of the ATP-dependent ClpCP protease in Bacillus subtilis. MecA contains two domains. Although the amino-terminal domain of MecA recruits substrate proteins such as ComK and ComS, the carboxyl-terminal domain (residues 121-218) has dual roles in the regulation and function of ClpCP protease. MecA-(121-218) facilitates the assembly of ClpCP oligomer, which is required for the protease activity of ClpCP. This domain was identified to be a non-recycling degradation tag that targets heterologous fusion proteins to the ClpCP protease for degradation. To elucidate the mechanism of MecA, we determined the crystal structure of MecA-(121-218) at 2.2 A resolution, which reveals a previously uncharacterized alpha/beta fold. Structure-guided mutagenesis allows identification of surface residues that are essential for the function of MecA. We also solved the structure of a carboxyl-terminal domain of YpbH, a paralogue of MecA in B. subtilis, at 2.4 A resolution. Despite low sequence identity, the two structures share essentially the same fold. The presence of MecA homologues in other bacterial species suggests conservation of a large family of unique degradation tags.
Ministry of Education Protein Science Laboratory, Tsinghua University, Beijing 100084, China.
Feng
F
Wang
Ziqing
Z
Mei
Yutao
Y
Qi
Chuangye
C
Yan
Siheng
S
Xiang
Zhiyuan
Z
Zhou
Qi
Q
Hu
Jiawei
J
Wang
Yigong
Y
Shi
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry*; D002850:Chromatography, Gel; D018360:Crystallography, X-Ray / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010447:Peptide Hydrolases / Q000737:chemistry; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; C083616:mecA protein, Bacillus subtilis; D010447:Peptide Hydrolases