Oral routes of administration for therapeutic peptides and proteins face two major barriers: proteolytic degradation in the stomach and an inadequate absorption mechanism for polypeptides within the intestinal lumen. As a result, peptide-based therapeutics are administered by injection, a painful process associated with lower patient compliance. The development of a means of overcoming these two major obstacles and enabling the successful delivery of peptide therapeutics by the oral route of administration has therefore been the target of extensive scientific endeavor. This Minireview focuses on oral peptide/protein delivery by the dietary uptake pathway for vitamin B(12). Recent progress in this field includes the delivery of erythropoietin, granulocyte-colony-stimulating factor, luteinizing-hormone-releasing hormone, and insulin.

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The unifying structural characteristic of members of the bacterial order Thermotogales is their toga, an unusual cell envelope that includes a loose-fitting sheath around each cell. Only two toga-associated structural proteins have been purified and characterized in Thermotoga maritima : the anchor protein OmpA1 (or Ompα) and the porin OmpB (or Ompβ). The gene encoding OmpA1 ( ompA1 ) was cloned and sequenced and later assigned to TM0477 in the genome sequence, but because no peptide sequence was available for OmpB, its gene ( ompB ) was not annotated. We identified six porin candidates in the genome sequence of T. maritima . Of these candidates, only one, encoded by TM0476, has all the characteristics reported for OmpB and characteristics expected of a porin including predominant β-sheet structure, a carboxy terminus porin anchoring motif, and a porin-specific amino acid composition. We highly enriched a toga fraction of cells for OmpB by sucrose gradient centrifugation and hydroxyapatite chromatography and analyzed it by LC/MS/MS. We found that the only porin candidate that it contained was the TM0476 product. This cell fraction also had β-sheet character as determined by circular dichroism, consistent with its enrichment for OmpB. We conclude that TM0476 encodes OmpB. A phylogenetic analysis of OmpB found orthologs encoded in syntenic locations in the genomes of all but two Thermotogales species. Those without orthologs have putative isofunctional genes in their place. Phylogenetic analyses of OmpA1 revealed that each species of the Thermotogales has one or two OmpA homologs. T. maritima has two OmpA homologs, encoded by ompA1 (TM0477) and ompA2 (TM1729), both of which were found in the toga protein-enriched cell extracts. These annotations of the genes encoding toga structural proteins will guide future examinations of the structure and function of this unusual lineage-defining cell sheath.

We recently reported a vitamin B(12) (B(12)) based insulin conjugate that produced significantly decreased blood glucose levels in diabetic STZ-rat models. The results of this study posed a fundamental question, namely what implications does B(12) conjugation have on insulin's interaction with the insulin receptor (IR)? To explore this question we used a combination of molecular dynamics simulations and immunoelectron microscopy, and the results are described herein. This investigation demonstrates that chemical modification of insulin by linking relatively large pendant groups does not inherently interfere with IR recognition. Furthermore, given that we have previously demonstrated a significant drop in blood glucose concentration following the oral administration of the B(12)-insulin bioconjugate used in this work, it is reasonable to conclude that the IR recognition described herein is associated with maintenance of biological activity for insulin. This outcome offers significant research scope for chemical modification of insulin with the purpose of improving oral-uptake efficiency.

Two previously uncharacterized potential broad-spectrum mercury (Hg) resistance operons (mer) are present on the chromosome of the soil Alphaproteobacteria Xanthobacter autotrophicus Py2. These operons, mer1 and mer2, contain two features which are commonly found in mer operons in the genomes of soil and marine Alphaproteobacteria, but are not present in previously characterized mer operons: a gene for the mercuric reductase (MerA) that encodes an alkylmercury lyase domain typical of those found on the MerB protein, and the presence of an additional gene, which we are calling merK, with homology to glutathione reductase. Here, we demonstrate that Py2 is resistant to 0.2 M inorganic mercury [Hg(II)] and 0.05 M methylmercury (MeHg). Py2 is capable of converting MeHg and Hg(II) to elemental mercury [Hg(0)], and reduction of Hg(II) is induced by incubation in sub toxic concentrations of Hg(II). Transcription of the merA genes increased with Hg(II) treatment, and in both operons merK resides on the same polycistronic mRNA as merA. We propose the use of Py2 as a model system for studying the contribution of mer to Hg mobility in soil and marine ecosystems. Bacterial mercury (Hg) resistance genes (mer) are important drivers in the biogeochemical cycle of Hg. These operons catalyze the conversion of inorganic mercury [Hg(II)] and sometimes methylmercury (MeHg) to elemental mercury [Hg(0)] (1). MeHg, which is more toxic than Hg(II) or Hg(0), is the form that biomagnifies in aquatic food webs (2, 3) and can cause toxicity to humans and animals that consume contaminated fish (4-6). Hg(II) is water soluble but sorbs strongly onto iron oxides and interacts with dissolved organic matter (7). Hg(0), the least toxic form, is both a liquid and a gas at room temperature and can evaporate from surface waters and soils (8, 9).All mer operons contain a gene encoding mercuric reductase, MerA, which converts Hg(II) to Hg(0), thereby conferring resistance (10). Some mer operons, called broad-spectrum mer operons, contain an additional gene encoding MerB, or alkylmercury lyase (AML), which degrades MeHg to Hg(II) and methane (11). Many mer operons contain genes for the transcriptional regulators MerR and MerD (12), as well the Hg transporters encoded by merT, merC, and merF, as well as additional Hg transfer proteins encoded by merP and merE (11, 13). Regulation of mer and the enzymatic activity of MerA is known in great detail for some operons and enzymes (10).It has been demonstrated that mer can influence the Hg cycle in lakes (14), but at present we know much less about the contribution of mer to the Hg cycle in soil and the terrestrial subsurface. It was long thought that Hg was relatively immobile in the subsurface due to sorption on sediment components such as iron oxides (1), but this assumption has come under scrutiny, since Hg has been unexpectedly found in groundwater at numerous sites, such as the Kirkwood-Cohansey aquifer in New Jersey (15, 16), the Waquoit Bay near Cape Cod, MA (17), and the coasts of California, northern ...

Mehrere Faktoren machen die orale Verabreichung von Peptiden und Proteinen zu einem Hauptziel der Wirkstoffaufnahme.[1] Um die Herausforderungen zu meistern, die sich aus dem Transport, der Permeabilität, der gastrointestinalen Stabilität und der Größe von Proteinmolekülen ergeben, wurden unterschiedliche Wege untersucht. Im Rahmen dieses Kurzaufsatzes konzentrieren wir uns auf das Aufnahmesystem von Vitamin B 12 (Cobalamin), das in den letzten 10 Jahre verstärkt beachtet wurde. Vitamin B 12 (kurz: B 12