Understanding the relationship between the metallocofactor and its protein environment is the key to uncovering the mechanism of metalloenzymes. PqqE, a radical S-adenosylmethionine enzyme in pyrroloquinoline quinone (PQQ) biosynthesis, contains three iron−sulfur cluster binding sites. Two auxiliary iron−sulfur cluster binding sites, designated as AuxI and AuxII, use distinctive ligands compared to other proteins in the family while their functions remain unclear. Here, we investigate the electronic properties of these iron−sulfur clusters and compare the catalytic efficiency of wild-type (WT) Methylorubrum extorquens AM1 PqqE to a range of mutated constructs. Using native mass spectrometry, protein film electrochemistry, and electron paramagnetic resonance spectroscopy, we confirm the previously proposed incorporation of a mixture of [2Fe-2S] and [4Fe-4S] clusters at the AuxI site and are able to assign redox potentials to each of the three iron− sulfur clusters. Significantly, a conservative mutation at AuxI, C268H, shown to selectively incorporate a [4Fe-4S] cluster, catalyzes an enhancement of uncoupled S-adenosylmethionine cleavage relative to WT, together with the elimination of detectable peptide cross-linked product. While a [4Fe-4S] cluster can be tolerated at the AuxI site, the aggregate findings suggest a functional [2Fe-2S] configuration within the AuxI site. PqqE variants with nondestructive ligand replacements at AuxII also show that the reduction potential at this site can be manipulated by changing the electronegativity of the unique aspartate ligand. A number of novel mechanistic features are proposed based on the kinetic and spectroscopic data. Additionally, bioinformatic analyses suggest that the unique ligand environment of PqqE may be relevant to its role in PQQ biosynthesis within an oxygen-dependent biosynthetic pathway.

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The screw drilling tool is an important underground power tool in the oil fields. During the working process, the rotor will be damaged or unevenly worn. The repair and reuse of the damaged area of the rotor will greatly improve the utilization rate of the screw drilling tool and reduce the mining cost. To this end, based on the formation principle of the rotor surface of the five-head screw drill, the curve coordinates are described by the ray length and the rotation angle. The axis relationship equation is characterized by exploring the intrinsic relationship between the two coordinates, and the reverse model of a single screw drill rotor was constructed by point collection. At the same time, the experimental research was carried out to verify the feasibility of modeling the screw drilling tool according to the axial section. In order to provide an effective way to reverse the entire body based on the unworn area of the screw drilling tool, the inverse modeling theory of the spiral surface entity is greatly enriched.