Many natural products contain the hexahydropyrrolo[2, 3-b]indole (HPI) framework. HPI containing chemicals exhibit various biological activities and distinguishable structural arrangement. This structural complexity renders chemical synthesis very challenging. Here, through investigating the biosynthesis of a naturally occurring C3-aryl HPI, naseseazine C (NAS-C), we identify a P450 enzyme (NascB) and reveal that NascB catalyzes a radical cascade reaction to form intramolecular and intermolecular carbon–carbon bonds with both regio- and stereo-specificity. Surprisingly, the limited freedom is allowed in specificity to generate four types of C3-aryl HPI scaffolds, and two of them were not previously observed. By incorporating NascB into an engineered strain of E. coli, we develop a whole-cell biocatalysis system for efficient production of NAS-C and 30 NAS analogs. Interestingly, we find that some of these analogs exhibit potent neuroprotective properties. Thus, our biocatalytic methodology offers an efficient and simple route to generate difficult HPI framework containing chemicals.

Owing to the high mortality and the spread rate, the infectious disease caused by SARS-CoV-2 has become a major threat to public health and social economy, leading to over 70 million infections and 1. 6 million deaths to date. Since there are currently no effective therapeutic or widely available vaccines, it is of urgent need to look for new strategies for the treatment of SARS-CoV-2 infection diseases. Binding of a viral protein onto cell surface heparan sulfate (HS) is generally the first step in a cascade of interaction that is required for viral entry and the initiation of infection. Meanwhile, interactions of selectins and cytokines (e.g., IL-6 and TNF-α) with HS expressed on endothelial cells are crucial in controlling the recruitment of immune cells during inflammation. Thus, structurally defined heparin/HS and their mimetics might serve as potential drugs by competing with cell surface HS for the prevention of viral adhesion and modulation of inflammatory reaction. In this review, we will elaborate coronavirus invasion mechanisms and summarize the latest advances in HS–protein interactions, especially proteins relevant to the process of coronavirus infection and subsequent inflammation. Experimental and computational techniques involved will be emphasized.

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We study the problem of gathering information from the nodes of a multi-hop radio network into a predefined destination node under reachability and interference constraints. In such a network, a node is able to send messages to other nodes within reception distance, but doing so it might create interference with other communications. Thus, a message can only be properly received if the receiver is reachable from the sender and there is no interference from another message being simultaneously transmitted. The network is modeled as a graph, where the vertices represent the nodes of the network and the edges, the possible communications. The interference constraint is modeled by a fixed integer d ≥ 1, which implies that nodes within distance d in the graph from one sender cannot receive messages from another node. In this paper, we suppose that each node has one unit-length message to transmit and, furthermore, we suppose that it takes one unit of time (slot) to transmit a unit-length message and during such a slot we can have only calls which do not interfere (called compatible calls). A set of compatible calls is referred to as a round. We give protocols and lower bounds on the minimum number of rounds for the gathering problem when the network is a path and the destination node is either at one end or at the center of the path. The protocols are shown to be optimal for any d in the first case, and for 1 ≤ d ≤ 4, in the second case.

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Anthrabenzoxocinones (ABXs) including (-)-ABXs and (+)-ABXs are a group of bacterial FabF-specific inhibitors with potent antimicrobial activity of resistant strains. Optimization of their chemical structures is a promising method to develop potent antibiotics. Through biosynthetic investigation, we herein identified and characterized two highly promiscuous enzymes involved in the (-)-ABX structural modification. The promiscuous halogenase and methyltransferase can respectively introduce halogen-modifications into various positions of the ABX scaffolds and methylation to highly diverse substrates. Manipulation of their activity in both of the (-)-ABXs and (+)-ABXs biosyntheses led to the generation of 14 novel ABX analogues of both enantiomers. Bioactivity assessment revealed that a few of the analogues showed significantly improved antimicrobial activity, with the C3-hydroxyl and chlorine substitutions critical for their activity. This study enormously expands the bioactive chemical space of the ABX family and FabF-specific inhibitors. The disclosed broad-selective biosynthetic machineries and structure-activity relationship provide a solid basis for further generation of potent antimicrobial agents.

Lactate racemase (LarA), a new nickel enzyme discovered recently, catalyzes the racemization between d- and l-lactates with a novel nickel pincer cofactor (Ni-PTTMN) derived from nicotinic acid. In this study, by using DFT and a 200-atom active-site model, LarA is revealed to employ a modified proton-coupled hydride-transfer mechanism in which a hydride is transferred to a cofactor pyridine carbon from the substrate α-carbon along with proton transfer from the substrate hydroxy group to a histidine, and then moved back from the opposite side. Tyr294 and Lys298 provide significant acceleration effects by orientating substrates and stabilizing the negative charge developing at the substrate hydroxy oxygen. The barrier was determined to be 12.0 kcal mol , which reveals enhanced racemase activity relative to the LarA reaction using NAD -like cofactors. Compared with NAD , Ni-PTTMN has a stronger hydride-addition reactivity in moderate and high environmental polarity and may fit perfectly the moderately polar active site of LarA.