Two distinct peptides

The last class, represented by E. coli 11 , consists of a membrane domain involving two distinct peptides, one very hydrophobic, and one somewhat less hydrophobic. The domains A and B are not covalently attached to the membrane domains but are separate cytoplasmic proteins [25,107], Other representatives of this class include B. subtilis [26] and K. pneumoniae II " [8],... 

Since its discovery, isolation, and purification in the early twentieth century, insulin has been administered to diabetic patients exclusively by injection until the recent introduction of inhaled insulin. Insulin possesses certain physiochemical properties that contribute to its limited absorption from the gastrointestinal tract, and requires subcutaneous injection to achieve clinically relevant bioavailability. With a molecular size of 5.7 kDa, insulin is a moderately sized polypeptide composed of two distinct peptide chains designated the A chain (21 amino acid residues) and the B chain (30 amino acid residues) and joined by two disulfide bonds. Like all polypeptides, insulin is a charged molecule that cannot easily penetrate the phospholipid membrane of the epithelial cells that line the nasal cavity. Furthermore, insulin monomers self-associate into hexameric units with a molecular mass greater than 30 kDa, which can further limit its passive absorption. Despite these constraints, successful delivery of insulin via the nasal route has been reported in humans and animals when an absorption enhancer was added to the formulation. 

Two of the most abundant endogenous opioid peptides, methionine-enkephalin (Met-enk Tyr-Gly-Gly-Phe-Met) and leucine-enkephalin (Leu-enk Tyr-Gly-Gly-Phe-Leu) are derived from the precursor protein, proenkephalin (PENK). PENK is a 267 amino acid precursor that contains 6 copies of Met-enk, two of which are extended forms (Tyr-Gly-Gly-Phe-Met-Arg-Phe and Tyr-Gly-Gly-Phe-Met-Arg-Gly-Leu) and one copy of Leu-enk. This ratio is essentially the same as the ratio of these peptides found in brain and adrenal chromaffin cells. The fact that there are two distinct peptides closely related in stmcture and function proved to be a major obstacle that slowed their discovery (Kosterlitz and Hughes, 1977). 

Roberge, M., Peek, M., Kirchhofer, D., Dennis, M. S., and Lazarus, R. A. 2002. Fusion of two distinct peptide exosite inhibitors of Factor Vila. Biochem, 363 387-93. 

When two or more distinct peptide chains are involved, the nature of their interactions can be quite complicated. Multimeric proteins with more than one kind of subunit often display different affinities between different pairs of sub-... 

Here, two different sequences from transth3Tetin were successfully combined into mixed fibrils [54], This is not always the case, however. For amyloidogenic proteins, the ability of other fibrils to act as cross-seeds for growth is known to depend on sequence similarity [55]. Seeding hen lysozyme solutions with seeds formed from closely related sequences (e.g. hen and other lysozymes) led to the largest increases in the rate of formation of fibrils. Consequently, there may be some restrictions on the selection of distinct peptide sequences to produce scaffolds. 

Cowgill pointed out that there are essentially two distinct quenching processes of tyrosine fluorescence resulting from association with the peptide bond.(3) Tyrosines affected by these mechanisms are classified in Table 1.3 as... 

Normal horse haemoglobin is a mixture of two distinct haemoglobins which arc present in approximately equal proportions. The nature of the chemical difference between the two components seems to reside in a single peptide. Crystallographically the two components appear to be identical and no differences can be ob.serv ed in the intensities of the X-ray reflections (36). At a resolution of 5.5 A the electron density maps of the two components should be identical. Horse oxy haemoglobin ciystallized... 

Yu F, Morin X, Cai Y, Yang X, Chia W (2000) Analysis of partner of inscuteable, a novel player of Drosophila asymmetric divisions, reveals two distinct steps in inscuteable apical localization. Cell 100 399 09 Zarling AL, Ficarro SB, White FM, Shabanowitz J, Hunt DF, Engelhard VH (2000) Phosphorylated peptides are naturally processed and presented by major histocompatibihty complex class I molecules in vivo. J Exp Med 192 1755-1762... 

Peptides are short chains of amino acids. By combining in various ways, two or more of the over 20 amino acids that are made by ail cells, a very large amount of chemical diversity can be generated. Some species of simple organisms such as the bacteria and the cyanobacteria make a number of distinct peptides, each species producing a different mixture. Some of these molecules have been shown to possess biological activity in certain test systems hence these peptides could be considered as NPs. Interestingly, the biosynthesis of these peptides has been compared, as has the biosynthesis of other NPs (see Chapter 5), with nature s version of the chemist s attempts to maximise the production of chemical diversity. ... 

Chymotrypsin enhances the rate of peptide bond hydrolysis by a factor of at least 109. It does not catalyze a direct attack of water on the peptide bond instead, a transient covalent acyl-enzyme intermediate is formed. The reaction thus has two distinct phases. In the acylation phase, the peptide bond is cleaved and an ester linkage is formed between the peptide carbonyl carbon and the enzyme. In the deacylation phase, the ester linkage is hydrolyzed and the nonacylated enzyme regenerated. 

As a result of the branched chain architecture, TASP molecules exhibit some unique conformational properties)5 12-14 47 75 76 148 For example, the folding to a compact state proceeds via two distinct steps the onset of secondary structure in the attached peptide blocks followed by their template-directed self-assembly to a three-dimensional packing topology. Due to its characteristic branched chain connectivity, the conformational space accessible in the unfolded state is considerably reduced compared to a linear chain of similar size (excluded volume effect), resulting in a smaller chain entropy. Thus, folded TASP molecules are expected to show higher thermodynamic stability compared to unbranched polypeptides of comparable size. 

Ferru, I., Georges, B., Bossus, M., Estaquier, J., Delacre, M., Harn, D.A., Tartar, A., Capron, A., Grassmasse, H. and Auriault, C. (1 997) Analysis of the immune response elicited by a multiple antigen peptide (MAP) composed of two distinct protective antigens derived from the parasite Schistosoma mansoni. Parasite Immunology 19, 1-11. 

Green, K. N., and Peers, C. (2002). Divergent pathways account for two distinct effects of amyloid beta peptides on exocytosis and Ca(2+) currents involvement of ROS and NF-kappaB. J Neurochem 81, 1043-1051. 

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