Metal-organic frameworks comprising metal-carboxylate cluster vertices and long, branched organic linkers are the most porous materials known, and therefore have attracted tremendous attention for many applications, including gas storage, separations, catalysis and drug delivery. To increase metal-organic framework porosity, the size and complexity of linkers has increased. Here we present a promising alternative strategy for constructing mesoporous metal-organic frameworks that addresses the size of the vertex rather than the length of the organic linker. This approach uses large metal-biomolecule clusters, in particular zinc-adeninate building units, as vertices to construct bio-MOF-100, an exclusively mesoporous metal-organic framework. Bio-MOF-100 exhibits a high surface area (4,300 m² g⁻¹), one of the lowest crystal densities (0.302 g cm⁻³) and the largest metal-organic framework pore volume reported to date (4.3 cm³ g⁻¹).

Summary: Iron is an essential element for almost all organisms, although an overload of this element results in toxicity because of the formation of hydroxyl radicals. Consequently, most living entities have developed sophisticated mechanisms to control their intracellular iron concentration. In many bacteria, including the opportunistic pathogen Pseudomonas aeruginosa, this task is performed by the ferric uptake regulator (Fur). Fur controls a wide variety of basic physiological processes including iron uptake systems and the expression of exotoxin A. Here, we present the first crystal structure of Fur from P. aeruginosa in complex with Zn²⁺ determined at a resolution of 1.8 Å. Furthermore, X‐ray absorption spectroscopic measurements and microPIXE analysis were performed in order to characterize the distinct zinc and iron binding sites in solution. The combination of these complementary techniques enables us to present a model for the activation and DNA binding of the Fur protein.

Members of the ferric/zinc uptake regulator (Fur/Zur) family are the central metal-dependent regulator proteins in many Gram-negative and -positive bacteria. They are responsible for the control of a wide variety of basic physiological processes and the expression of important virulence factors in human pathogens. Therefore, Fur has gathered significant interest as a potential target for novel antibiotics. Here we report the crystal structure of FurB from Mycobacterium tuberculosis at a resolution of 2.7A, and we present biochemical and spectroscopic data that allow us to propose the functional role of this protein. Although the overall fold of FurB with an N-terminal DNA binding domain and a C-terminal dimerization domain is conserved among the Zur/Fur family, large differences in the spatial arrangement of the two domains with respect to each other can be observed. The biochemical and spectroscopic analysis presented here reveals that M. tuberculosis FurB is Zn(II)-dependent and is likely to control genes involved in the bacterial zinc uptake. The combination of the structural, spectroscopic, and biochemical results enables us to determine the structural basis for functional differences in this important family of bacterial regulators.