Liposomes are versatile three‐dimensional, biomaterial‐based frameworks that can spatially enclose a variety of organic and inorganic biomaterials for advanced targeted‐delivery applications. Implementation of external‐stimuli‐controlled release of their cargo will significantly augment their wide application for liposomal drug delivery. This paper presents the synthesis of a carbohydrate‐derived lipid, capable of changing its conformation depending on the presence of Zn2+: an active state in the presence of Zn2+ ions and back to an inactive state in the absence of Zn2+ or when exposed to Na2EDTA, a metal chelator with high affinity for Zn2+ ions. This is the first report of a lipid triggered by the presence of a metal chelator. Total internal reflection fluorescence microscopy and a single‐liposome study showed that it indeed was possible for the lipid to be incorporated into the bilayer of stable liposomes that remained leakage‐free for the fluorescent cargo of the liposomes. On addition of EDTA to the liposomes, their fluorescent cargo could be released as a result of the membrane‐incorporated lipids undergoing a conformational change.
Chemical modification of proteins has numerous applications, but it has been challenging to achieve the required high degree of selectivity on lysine amino groups. Recently, we described the highly selective acylation of proteins with an N‐terminal Gly‐His6 segment. This tag promoted acylation of the N‐terminal Nα‐amine resulting in stable conjugates. Herein, we report the peptide sequences Hisn‐Lys‐Hism, which we term Lys‐His tags. In combination with simple acylating agents, they facilitate the acylation of the designated Lys Nϵ‐amine under mild conditions and with high selectivity over native Lys residues. We show that the Lys‐His tags, which are 7 to 10 amino acids in length and still act as conventional His tags, can be inserted in proteins at the C‐terminus or in loops, thus providing high flexibility regarding the site of modification. Finally, the selective and efficient acylation of the therapeutic antibody Rituximab, pure or mixed with other proteins, demonstrates the scope of the Lys‐His tag acylation method.
Receptors that distinguish the multitude of microbes surrounding plants in the environment enable dynamic responses to the biotic and abiotic conditions encountered. In this study, we identify and characterise a glycan receptor kinase, EPR3a, closely related to the exopolysaccharide receptor EPR3. Epr3a is up-regulated in roots colonised by arbuscular mycorrhizal (AM) fungi and is able to bind glucans with a branching pattern characteristic of surface-exposed fungal glucans. Expression studies with cellular resolution show localised activation of the Epr3a promoter in cortical root cells containing arbuscules. Fungal infection and intracellular arbuscule formation are reduced in epr3a mutants. In vitro, the EPR3a ectodomain binds cell wall glucans in affinity gel electrophoresis assays. In microscale thermophoresis (MST) assays, rhizobial exopolysaccharide binding is detected with affinities comparable to those observed for EPR3, and both EPR3a and EPR3 bind a well-defined β-1,3/β-1,6 decasaccharide derived from exopolysaccharides of endophytic and pathogenic fungi. Both EPR3a and EPR3 function in the intracellular accommodation of microbes. However, contrasting expression patterns and divergent ligand affinities result in distinct functions in AM colonisation and rhizobial infection in Lotus japonicus. The presence of Epr3a and Epr3 genes in both eudicot and monocot plant genomes suggest a conserved function of these receptor kinases in glycan perception.
Metal ion-induced self-assembly (SA) of proteins into higher-order structures can provide new, dynamic nano-assemblies. Here, the synthesis and characterization of a human insulin (HI) analog modified at LysB29 with the...
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