Structure and mechanism of an antibiotics-synthesizing 3-hydroxykynurenine C-methyltransferase

Abstract

Streptosporangium sibiricum SibL catalyzes the methyl transfer from S-adenosylmethionine (SAM) to 3-hydroxykynurenine (3-HK) to produce S-adenosylhomocysteine (SAH) and 3-hydroxy-4-methyl-kynurenine for sibiromycin biosynthesis. Here, we present the crystal structures of apo-form Ss-SibL, Ss-SibL/SAH binary complex and Ss-SibL/SAH/3-HK ternary complex. Ss-SibL is a homodimer. Each subunit comprises a helical N-terminal domain and a Rossmann-fold C-terminal domain. SAM (or SAH) binding alone results in domain movements, suggesting a two-step catalytic cycle. Analyses of the enzyme-ligand interactions and further mutant studies support a mechanism in which Tyr134 serves as the principal base in the transferase reaction of methyl group from SAM to 3-HK.

Anisotropic effect of warping on the lifetime broadening of topological surface states in angle-resolved photoemission fromBi2Te3

“…From temperature-dependent measurements in our own Bi 2 Te 3 samples we find a weak electron-phonon coupling characterized by λ ≈ 0.17, in agreement with recent studies. 47 This result leads to Σ e−ph ≈ 2 meV, which represents an almost negligible energy-independent contribution to the lifetime broadening due to electron-phonon interaction. Other contributions to the linewidths due to final-state broadening, which for two-dimensional electronic states are reduced to an extra broadening of purely geometrical origin, 36,37 are also negligible.…”

“…This assumption is valid under the approximation in which v 0 is the renormalized group velocity v g , implying that the real part of the selfenergy Σ is small, in agreement with recent observations on TSSs where a weak renormalization due to electronphonon coupling in the vicinity of the Fermi level and slowly varying energy-dependent values of Σ have been found. 45,47 We point out that due to such a BE dependence of Σ , 45,47 the surface-state peaks still show a slight asymmetry with increasing BE, but by fitting MDCs with convoluted Lorentzian functions we have nevertheless obtained accurate results.…”

“…Nevertheless, in our case we find a low-background signal and rather symmetric peaks across the Fermi level, in a similar fashion as in previous studies. [45][46][47]52 The Σ values, which are directly represented by the HWHM of the Lorentzian peaks obtained by fitting the corresponding EDCs, are shown in Fig. 4 (c) for both ΓK [blue (dark) circles] and ΓM [red (light) circles] highsymmetry directions.…”

“…ARPES represents an ideal technique for such a purpose, as it is a well-established method to determine the lifetime broadening of electronic states, 36,37 not only in strongly correlated systems such as transition-metal oxides, 38 4f rare-earths, 39 high-T c superconductors 40,41 or 3d ferromagnets, [42][43][44] but also in TIs. [45][46][47] Moreover, ARPES has recently become the most powerful tool in systematically revealing the linear dispersion of TSSs in energy and momentum space.…”

Selection of multi-criteria plant layout design by combining AHP and DEA methodologies

“…Ojaghi et al [6] minimized travel distance, material handling and losses of company producing meatball and soup paste by using SLP to generate new layouts. Chen et al [7] adopted SLP approach to enhance the performance on optimizing the layout design of a large auto parts manufacturing enterprise. In this study, AHP was adopted to evaluate optimal layout.…”