Prevalence and mechanism of synergistic carboxylate-cation-water interactions in halophilic proteins.

The cytoplasmic proteins of some halophilic organisms remain stable and functional at multimolar concentrations of KCl, i.e., under conditions that most mesophilic proteins cannot withstand. Their stability arises from their unusual amino acid composition. The most dramatic difference between halophilic and mesophilic proteins is that the former are rich in acidic amino acids. It has been proposed that one of the evolutionary driving forces for this difference is the occurrence of synergistic interactions between multiple acidic amino acids at the surface of the protein, the potassium cations in solution, and water. We investigate this possibility with molecular dynamics simulations, using high-quality force fields for the protein-water, protein-ion, and ion-ion interactions. We create a rigorous thermodynamic definition of interactions between acidic amino acids on proteins that can be used to distinguish between synergistic, noninteracting and interfering interactions. Our results demonstrate that synergistic interactions between neighboring acidic amino acids in halophilic proteins are frequent at multimolar KCl concentration. Synergistic interactions have an electrostatic origin, and are associated with stronger water-to-carboxylate hydrogen bonds than for acidic amino acids without synergistic interactions. Synergistic interactions are not observed in minimal systems of carboxylates, indicating that the protein environment is critical for their emergence. Our results demonstrate that synergistic interactions are neither associated with rigid amino acid orientations nor with highly structured and slow moving water networks, as had been originally proposed. Moreover, synergistic interactions can also be found in unfolded protein conformations. However, because these conformations are only a small subset of the unfolded state ensemble, synergistic interactions should contribute to the net stabilization of the folded state.

How acidic amino acid residues facilitate DNA target site selection.

Despite the negative charge of the DNA backbone, acidic residues (Asp/Glu) commonly participate in the base readout, with a strong preference for cytosine. In fact, in the solved DNA/protein structures, cytosine is recognized almost exclusively by Asp/Glu through a direct hydrogen bond, while at the same time, adenine, regardless of its amino group, shows no propensity for Asp/Glu. Here, we analyzed the contribution of Asp/Glu to sequence-specific DNA binding using classical and ab initio simulations of selected transcription factors and found that it is governed by a fine balance between the repulsion from backbone phosphates and attractive interactions with cytosine. Specifically, Asp/Glu lower the affinity for noncytosine sites and thus act as negative selectors preventing off-target binding. At cytosine-containing sites, the favorable contribution does not merely rely on the formation of a single H-bond but usually requires the presence of positive potential generated by multiple cytosines, consistently with the observed excess of cytosine in the target sites. Finally, we show that the preference of Asp/Glu for cytosine over adenine is a result of the repulsion from the adenine imidazole ring and a tendency of purine-purine dinucleotides to adopt the BII conformation.

Prediction of Quality-control Degradation Signals in Yeast Proteins.

Effective proteome homeostasis is key to cellular and organismal survival, and cells therefore contain efficient quality control systems to monitor and remove potentially toxic misfolded proteins. Such general protein quality control to a large extent relies on the efficient and robust delivery of misfolded or unfolded proteins to the ubiquitin-proteasome system. This is achieved via recognition of so-called degradation motifs-degrons-that are assumed to become exposed as a result of protein misfolding. Despite their importance, the nature and sequence properties of quality-control degrons remain elusive. Here, we have used data from a yeast-based screen of 23,600 17-residue peptides to build a predictor of quality-control degrons. The resulting model, QCDPred (Quality Control Degron Prediction), achieves good accuracy using only the sequence composition of the peptides as input. Our analysis reveals that strong degrons are enriched in hydrophobic amino acids and depleted in negatively charged amino acids, in line with the expectation that they are buried in natively folded proteins. We applied QCDPred to the yeast proteome, enabling us to analyse more widely the potential effects of degrons. As an example, we show a correlation between cellular abundance and degron potential in disordered regions of proteins. Together with recent results on membrane proteins, our work suggest that the recognition of exposed hydrophobic residues is a key and generic mechanism for proteome homeostasis. QCDPred is freely available as open source code and via a web interface.

Guanidinium-amino acid hydrogen-bonding interactions in protein crystal structures: implications for guanidinium-induced protein denaturation.

In the present work, 86 available high resolution X-ray structures of proteins that contain one or more guanidinium ions (Gdm+) are analyzed for the distribution and nature of noncovalent interactions between Gdm+ and amino-acid residues. A total of 1044 hydrogen-bonding interactions were identified, of which 1039 are N-H⋯O, and five are N-H⋯N. Acidic amino acids are more likely to interact with Gdm+ (46% of interactions, 26% Asp and 20% Glu), followed by Pro (19% of interactions). DFT calculations on the identified Gdm+-amino acid hydrogen-bonded pairs reveal that although Gdm+ interacts primarily with the backbone amides of nonpolar amino acids, Gdm+ does interact with the sidechains of polar and acidic amino acids. We classified the optimized Gdm+-amino acid pairs into parallel [p], bifurcated [b], single hydrogen bonded [s] and triple hydrogen bonded [t] types. The [p] and [t] type pairs possess higher average interaction strength that is stronger than that of [b] and [s] type pairs. Negatively charged aspartate and glutamate residues interact with Gdm+ ion exceptionally tightly (-76 kcal mol-1) in [p] type complexes. This work provides statistical and energetics insights to better describe the observed destabilization or denaturation process of proteins by guanidinium salts.

Functional differentiation determines the molecular basis of the symbiotic lifestyle of Ca. Nanohaloarchaeota.

BACKGROUND: Candidatus Nanohaloarchaeota, an archaeal phylum within the DPANN superphylum, is characterized by limited metabolic capabilities and limited phylogenetic diversity and until recently has been considered to exclusively inhabit hypersaline environments due to an obligate association with Halobacteria. Aside from hypersaline environments, Ca. Nanohaloarchaeota can also have been discovered from deep-subsurface marine sediments. RESULTS: Three metagenome-assembled genomes (MAGs) representing a new order within the Ca. Nanohaloarchaeota were reconstructed from a stratified salt crust and proposed to represent a novel order, Nucleotidisoterales. Genomic features reveal them to be anaerobes capable of catabolizing nucleotides by coupling nucleotide salvage pathways with lower glycolysis to yield free energy. Comparative genomics demonstrated that these and other Ca. Nanohaloarchaeota inhabiting saline habitats use a "salt-in" strategy to maintain osmotic pressure based on the high proportion of acidic amino acids. In contrast, previously described Ca. Nanohaloarchaeota MAGs from geothermal environments were enriched with basic amino acids to counter heat stress. Evolutionary history reconstruction revealed that functional differentiation of energy conservation strategies drove diversification within Ca. Nanohaloarchaeota, further leading to shifts in the catabolic strategy from nucleotide degradation within deeper lineages to polysaccharide degradation within shallow lineages. CONCLUSIONS: This study provides deeper insight into the ecological functions and evolution of the expanded phylum Ca. Nanohaloarchaeota and further advances our understanding on the functional and genetic associations between potential symbionts and hosts. Video Abstract.

Stable terbium metal-organic framework with turn-on and blue-shift fluorescence sensing for acidic amino acids (L-aspartate and L-glutamine) and cations (Al3+ and Ga3+).

A terbium-based metal-organic framework, namely {[Tb2(ADIP)(H2ADIP)(HCOOH)(H2O)2]·2DMF·2H2O}n (Tb-MOF, H4ADIP = 5,5'-(anthracene-9,10-diyl) diisophthalic acid), was synthesized and characterized. The single-crystal structure analysis shows that the Tb-MOF crystallizes in the C2/C space group in the monoclinic system and its asymmetric unit contains two TbIII ions, one ADIP4-, one H2ADIP2-, one coordinating formic acid and two coordination water molecules. Tb-MOF has a three-dimensional porous structure with a porosity of 41.5%. Tb-MOF is a highly selective and sensitive fluorescence turn-on and blue-shift sensor for L-aspartate (Asp), L-glutamine (Glu), Al3+ and Ga3+with detection limits of 0.25, 0.23, 0.069 and 0.079 µM, respectively. Experimental studies and theoretical calculations show that the sensing process is mainly attributed to the energy transfer and the absorbance caused enhancement (ACE) mechanism. Therefore, Tb-MOF is a good multi-response fluorescence sensor for acidic amino acids and Al3+, Ga3+cations.

Epitope Fine Mapping by Mass Spectrometry: Investigations of Immune Complexes Consisting of Monoclonal Anti-HpTGEKP Antibody and Zinc Finger Protein Linker Phospho-Hexapeptides.

Accurate formation of antibody-antigen complexes has been relied on in both, multitudes of scientific projects and ample therapeutic and diagnostic applications. Mass spectrometrically determined dissociation behavior of immune complexes with the anti-HpTGEKP antibody revealed that the ten most frequently occurring phospho-hexapeptide linker sequences from C2H2 zinc finger proteins could be divided into two classes: orthodox binders, where strong noncovalent interactions developed as anticipated, and unorthodox binders with deviating structures and weaker binding. Phosphorylation of threonine was compulsory for antibody binding in an orthodox manner. Gas phase dissociation energy determinations of seven C2H2 zinc finger protein linker phospho-hexapeptides with orthodox binding properties revealed a bipolar binding motif of the antibody paratope. Epitope peptides, which in addition to the negatively charged phospho-threonine residue were C-terminally flanked by positively charged residues provided stronger binding, i. e. dissociation was endothermic, than peptides with acidic amino acid residues at these positions, for which dissociation was exothermic.

Enhanced production of γ-amino acid 3-amino-4-hydroxybenzoic acid by recombinant Corynebacterium glutamicum under oxygen limitation.

BACKGROUND: Bio-based aromatic compounds are of great interest to the industry, as commercial production of aromatic compounds depends exclusively on the unsustainable use of fossil resources or extraction from plant resources. γ-amino acid 3-amino-4-hydroxybenzoic acid (3,4-AHBA) serves as a precursor for thermostable bioplastics. RESULTS: Under aerobic conditions, a recombinant Corynebacterium glutamicum strain KT01 expressing griH and griI genes derived from Streptomyces griseus produced 3,4-AHBA with large amounts of amino acids as by-products. The specific productivity of 3,4-AHBA increased with decreasing levels of dissolved oxygen (DO) and was eightfold higher under oxygen limitation (DO = 0 ppm) than under aerobic conditions (DO ≥ 2.6 ppm). Metabolic profiles during 3,4-AHBA production were compared at three different DO levels (0, 2.6, and 5.3 ppm) using the DO-stat method. Results of the metabolome analysis revealed metabolic shifts in both the central metabolic pathway and amino acid metabolism at a DO of < 33% saturated oxygen. Based on this metabolome analysis, metabolic pathways were rationally designed for oxygen limitation. An ldh deletion mutant, with the loss of lactate dehydrogenase, exhibited 3.7-fold higher specific productivity of 3,4-AHBA at DO = 0 ppm as compared to the parent strain KT01 and produced 5.6 g/L 3,4-AHBA in a glucose fed-batch culture. CONCLUSIONS: Our results revealed changes in the metabolic state in response to DO concentration and provided insights into oxygen supply during fermentation and the rational design of metabolic pathways for improved production of related amino acids and their derivatives.

Changing Gly311 to an acidic amino acid in the MATE family protein DTX6 enhances Arabidopsis resistance to the dihydropyridine herbicides.

In modern agriculture, frequent application of herbicides may induce the evolution of resistance in plants, but the mechanisms underlying herbicide resistance remain largely unexplored. Here, we report the characterization of rtp1 (resistant to paraquat 1), an Arabidopsis mutant showing strong resistance to the widely used herbicides paraquat and diquat. The rtp1 mutant is semi-dominant and carries a point mutation in the gene encoding the multidrug and toxic compound extrusion family protein DTX6, leading to the change of glycine to glutamic acid at residue 311 (G311E). The wild-type DTX6 with glycine 311 conferred weak paraquat and diquat resistance when overexpressed, while mutation of glycine 311 to a negatively charged amino acid (G311E or G311D) markedly increased the paraquat and diquat resistance of plants, whereas mutation to a positively charged amino acid (G311R or G311K) compromised the resistance, suggesting that the charge property of residue 311 of DTX6 is critical for the paraquat and diquat resistance of Arabidopsis plants. DTX6 is localized in the endomembrane trafficking system and may undergo the endosomal sorting to localize to the vacuole and plasma membrane. Treatment with the V-ATPase inhibitor ConA reduced the paraquat resistance of the rtp1 mutant. Paraquat release and uptake assays demonstrated that DTX6 is involved in both exocytosis and vacuolar sequestration of paraquat. DTX6 and DTX5 show functional redundancy as the dtx5 dtx6 double mutant but not the dtx6 single mutant plants were more sensitive to paraquat and diquat than the wild-type plants. Collectively, our work reveals a potential mechanism for the evolution of herbicide resistance in weeds and provides a promising gene for the manipulation of plant herbicide resistance.

Proteins maintain hydration at high [KCl] concentration regardless of content in acidic amino acids.

Proteins of halophilic organisms, which accumulate molar concentrations of KCl in their cytoplasm, have a much higher content in acidic amino acids than proteins of mesophilic organisms. It has been proposed that this excess is necessary to maintain proteins hydrated in an environment with low water activity, either via direct interactions between water and the carboxylate groups of acidic amino acids or via cooperative interactions between acidic amino acids and hydrated cations. Our simulation study of five halophilic proteins and five mesophilic counterparts does not support either possibility. The simulations use the AMBER ff14SB force field with newly optimized Lennard-Jones parameters for the interactions between carboxylate groups and potassium ions. We find that proteins with a larger fraction of acidic amino acids indeed have higher hydration levels, as measured by the concentration of water in their hydration shell and the number of water/protein hydrogen bonds. However, the hydration level of each protein is identical at low (bKCl = 0.15 mol/kg) and high (bKCl = 2 mol/kg) KCl concentrations; excess acidic amino acids are clearly not necessary to maintain proteins hydrated at high salt concentration. It has also been proposed that cooperative interactions between acidic amino acids in halophilic proteins and hydrated cations stabilize the folded protein structure and would lead to slower dynamics of the solvation shell. We find that the translational dynamics of the solvation shell is barely distinguishable between halophilic and mesophilic proteins; if such a cooperative effect exists, it does not have that entropic signature.

Acidic amino acids as counterions of ciprofloxacin: Effect on growth and pigment production in Staphylococcus aureus NCTC 8325 and Pseudomonas aeruginosa PAO1.

Antimicrobial resistance (AMR) is emerging as a global threat to public health. One of the strategies employed to combat AMR is the use of adjuvants which act to enhance or reinstate antimicrobial activity by inhibiting resistance mechanisms. However, these adjuvants are themselves not immune to selecting resistant phenotypes. Thus, there is a need to utilise mechanisms which are either less likely to or unable to trigger resistance. One commonly employed mechanism of resistance by microorganisms is to prevent antimicrobial uptake or efflux the antibiotic which manages to permeate its membrane. Here we propose amino acids as antimicrobial adjuvants that may be utilizing alternate mechanisms to fight AMR. We used a modified ethidium bromide (EtBr) efflux assay to determine its efflux in the presence of ciprofloxacin within Staphylococcus aureus (NCTC 8325) and Pseudomonas aeruginosa (PAO1). In this study, aspartic acid and glutamic acid were found to inhibit growth of both bacterial species. Moreover, a reduced production of toxic pigments, pyocyanin and pyoverdine by P. aeruginosa was also observed. As evident from similar findings with tetracycline, these adjuvants, may be a way forward towards tackling antimicrobial resistance.

Bone-Specific Drug Delivery for Osteoporosis and Rare Skeletal Disorders.

PURPOSE OF REVIEW: The skeletal system provides an important role to support body structure and protect organs. The complexity of its architecture and components makes it challenging to deliver the right amount of the drug into bone regions, particularly avascular cartilage lesions. In this review, we describe the recent advance of bone-targeting methods using bisphosphonates, polymeric oligopeptides, and nanoparticles on osteoporosis and rare skeletal diseases. RECENT FINDINGS: Hydroxyapatite (HA), a calcium phosphate with the formula Ca10(PO4)6(OH)2, is a primary matrix of bone mineral that includes a high concentration of positively charged calcium ion and is found only in the bone. This unique feature makes HA a general targeting moiety to the entire skeletal system. We have applied bone-targeting strategy using acidic amino acid oligopeptides into lysosomal enzymes, demonstrating the effects of bone-targeting enzyme replacement therapy and gene therapy on bone and cartilage lesions in inherited skeletal disorders. Virus or no-virus gene therapy using techniques of engineered capsid or nanomedicine has been studied preclinically for skeletal diseases. Efficient drug delivery into bone lesions remains an unmet challenge in clinical practice. Bone-targeting therapies based on gene transfer can be potential as new candidates for skeletal diseases.

Bone-Targeting Systems to Systemically Deliver Therapeutics to Bone Fractures for Accelerated Healing.

PURPOSE OF REVIEW: Compared with the current standard of implanting bone anabolics for fracture repair, bone fracture-targeted anabolics would be more effective, less invasive, and less toxic and would allow for control over what phase of fracture healing is being affected. We therefore sought to identify the optimal bone-targeting molecule to allow for systemic administration of therapeutics to bone fractures. RECENT FINDINGS: We found that many bone-targeting molecules exist, but most have been developed for the treatment of bone cancers, osteomyelitis, or osteoporosis. There are a few examples of bone-targeting ligands that have been developed for bone fractures that are selective for the bone fracture over the body and skeleton. Acidic oligopeptides have the ideal half-life, toxicity profile, and selectivity for a bone fracture-targeting ligand and are the most developed and promising of these bone fracture-targeting ligands. However, many other promising ligands have been developed that could be used for bone fractures.

Acidic residues of extracellular loop 3 of the Na+/H+ exchanger type 1 are important in cation transport.

Mammalian Na+/H+ exchanger type I isoform (NHE1) is a ubiquitously expressed membrane protein that regulates intracellular pH (pHi) by removing one intracellular proton in exchange for one extracellular sodium ion. Abnormal activity of the protein occurs in cardiovascular disease and breast cancer. The purpose of this study is to examine the role of negatively charged amino acids of extracellular loop 3 (EL3) in the activity of the NHE protein. We mutated glutamic acid 217 and aspartic acid 226 to alanine, and to glutamine and asparagine, respectively. We examined effects on expression levels, cell surface targeting and activity of NHE1, and also characterized affinity for extracellular sodium and lithium ions. Individual mutation of these amino acids had little effect on protein function. However, mutation of both these amino acids together impaired transport, decreasing the Vmax for both Na+ and Li+ ions. We suggested that amino acids E217 and D226 form part of a negatively charged coordination sphere, which facilitates cation transport in the NHE1 protein.

Multiple draft tubes airlift loop membrane bioreactor as an efficient system for acidic 7-amino cephalosporanic acid (7-ACA) wastewater treatment.

In this study, a lab-scale multiple draft tubes airlift loop membrane bioreactor (Mt-ALMBR) was used for treating acidic 7-amino cephalosporanic acid (7-ACA) wastewater under different pHs (3.54-6.20) and hydraulic retention time (HRT) (48 h, 36 h, 24 h and 16 h). During about 200 days operation, under HRT of 48 h and pH condition about 6.0, the optimum average COD and BOD5 removal rates were reach to 84.4 ± 2.1% and 94.9 ± 0.8%, and the highest 7-ACA removal rate also observed as 77.6%. Biodegradation, membrane rejection, hydrolysis and sludge adsorption were the four main pathways of 7-ACA removal. With the increase of pH, biodegradation, membrane rejection and hydrolysis had significant positive impacts on 7-ACA removal, while adsorption had a negative impact. Moreover, mathematical models for 7-ACA removal rate and pH were calculated to guide the operation of Mt-ALMBR. Biodegradation was the main pathway to remove 7-ACA when pH was >4.17.

Binding of the periplakin linker requires vimentin acidic residues D176 and E187.

Plakin proteins form connections that link the cell membrane to the intermediate filament cytoskeleton. Their interactions are mediated by a highly conserved linker domain through an unresolved mechanism. Here analysis of the human periplakin linker domain structure reveals a bi-lobed module transected by an electropositive groove. Key basic residues within the periplakin groove are vital for co-localization with vimentin in human cells and compromise direct binding which also requires acidic residues D176 and E187 in vimentin. We propose a model whereby basic periplakin linker domain residues recognize acidic vimentin side chains and form a complementary binding groove. The model is shared amongst diverse linker domains and can be used to investigate the effects of pathogenic mutations in the desmoplakin linker associated with arrhythmogenic right ventricular cardiomyopathy. Linker modules either act solely or collaborate with adjacent plakin repeat domains to create strong and adaptable tethering within epithelia and cardiac muscle.

D-Aspartate oxidase: distribution, functions, properties, and biotechnological applications.

Recently, substantial levels of acidic D-amino acids, such as D-aspartate and D-glutamate, have been identified in many organisms, from bacteria to mammals, suggesting that acidic D-amino acids have multiple physiological significances. Although acidic D-amino acids found in animals primarily originate from foodstuffs and/or bacteria, the D-aspartate-synthesizing enzyme aspartate racemase is identified in various animals. In eukaryotic organisms, acidic D-amino acids are primarily degraded by the flavoenzyme D-aspartate oxidase (DDO). DDO is found in multiple eukaryotic organisms and may play important roles in acidic D-amino acid utilization, elimination, and intracellular level regulation. Moreover, owing to its perfect enantioselectivity and stereoselectivity, DDO may be a valuable tool in several biotechnological applications, including the identification and quantification of acidic D-amino acids. In this mini-review, previous DDO reports are summarized and the potential bioengineering and biotechnological applications of DDO are discussed. Key Points ・Occurrence and distribution ofd-aspartate oxidase. ・Fundamental properties of d -aspartate oxidase of various eukaryotic organisms. ・Biotechnological applications and potential engineering ofd-aspartate oxidase.

pH-induced aggregation of hydrophilic carbon dots for fluorescence detection of acidic amino acid and intracellular pH imaging.

Intracellular pH level plays an important role in physiological and pathological processes. The development of nanoprobes for detecting in vivo pH levels is especially important for early diagnosis of disease. Therefore, we develop a hydrophilic carbon points (CDs) using quercetin and ethylenediamine as precursors to monitor intracellular pH. Under optimized conditions, the prepared CDs not only have uniform particle size and morphology, but also possess strong green fluorescence, photostability, and photoreversibility in water medium. The CDs exhibit pH-sensitive fluorescence effect under acidic and alkaline conditions, which is used to achieve "off-on-off" detection pH (from 3.5 to 13.5). Meanwhile, the pH-dependent mechanism is further investigated and explained, which is the fluorescence quenching caused by the pH-induced aggregation. Based on the pH-sensitive characteristics of CDs, it has been applied to the detection of aspartic acid and glutamic acid. More importantly, when applied to live cells, the pH-probe exhibits low cytotoxicity and high sensitivity, and is successfully used in intracellular pH fluorescence imaging. Consequently, this nanoprobe is expected to be used for real-time monitoring of intracellular pH level.

Volumetric, acoustic, viscometric, calorimetric and spectroscopic studies to elucidate the effects of citrate and tartrate based food preservatives on the solvation behaviors of acidic amino acids at different temperatures.

The effects of trisodium citrate (TSC) and disodium tartrate (DST) based food preservatives on the hydration behaviors of the amino acids l-aspartic acid (ASP) and l-glutamic acid (GLU) have been studied using thermodynamic, transport, calorimetric and spectroscopic studies. The volumetric, acoustic and viscosity data suggest that hydrophilic-ionic/hydrophilic interactions are predominant in these systems. The calculated parameters are worthwhile for exploring the solutes as structure-breakers, and the solutes undergo pairwise interactions with the co-solutes. The sweetness of both amino acids decreases in the presence of the preservatives. The hydration number and solvation data suggest that these solutes are more hydrated in water. The dominance of dehydration effects in relation to TSC is observed from the positive enthalpy changes in calorimetry studies and the negative chemical shifts in 1H NMR studies.

Colon-Targeted Delivery Facilitates the Therapeutic Switching of Sofalcone, a Gastroprotective Agent, to an Anticolitic Drug via Nrf2 Activation.

We investigated if the therapeutic switching of sofalcone (SFC), a gastroprotective agent, to an anticolitic agent is feasible using colon-targeted drug delivery. SFC can activate the anti-inflammatory nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-hemeoxygenase-1 (HO-1) pathway in human colon epithelial cells and murine macrophages. For the efficient treatment of colitis, SFC was coupled with acidic amino acids to yield SFC-aspartic acid (SFC-AA) and SFC-glutamic acid, and their colon targetability and therapeutic effects were assessed as an anticolitic agent in a 2,4-dinitrobenezenesulfonic acid-induced rat colitis model. The SFC derivatives were decoupled up to 72% in the cecal contents but remained stable in the small intestinal contents. Oral gavage of SFC-AA (oral SFC-AA, equivalent to 1.67 mg/kg of SFC) delivered SFC (maximal cecal concentration: 57.36 µM) to the cecum, while no SFC was detected with oral gavage of SFC (oral SFC, 1.67 mg/kg). Moreover, oral SFC-AA (equivalent to 10 mg/kg of SFC) did not afford detectable concentration of SFC in the blood but detected up to 4.64 µM with oral SFC (10 mg/kg), indicating efficient colonic delivery and limited systemic absorption of SFC upon oral SFC-AA. Oral SFC-AA ameliorated colonic damage and inflammation in rat colitis with elevating colonic levels of HO-1 and nuclear Nrf2 protein, and the anticolitic effects of SFC-AA were significantly undermined by an HO-1 inhibitor. At an equivalent dose of SFC, oral SFC-AA but not oral SFC increased colonic HO-1 and nuclear Nrf2 levels, and oral SFC-AA was more effective than oral SFC in treating rat colitis. Moreover, oral SFC-AA was as effective against colitis as oral sulfasalazine being used for the treatment of inflammatory bowel disease. In conclusion, colon-targeted delivery of SFC facilitated the therapeutic switching of the drug to an anticolitic drug via Nrf2 activation.