N-terminal amino acids

The 4TM receptors are pentameric complexes composed of subunits of 420 to 550 amino acids. The subunits exhibit sequence identities from 25 to 75%, with a similar distribution of hydrophobic and hydrophilic domains (Table 3.1). The hydrophilic 210 to 230 amino-acid N-terminal domain is followed by three closely spaced hydrophobic and putative transmembrane domains, then a variable-length intracellular loop, and finally a fourth putative transmembrane region shortly before the C-terminus (Figure 3.1). Of the four candidate transmembrane regions, evidence suggests that TM2 forms an a-helix, while the other hydrophobic regions more likely are folded as (3-sheets. 

The first protease inhibitor studied in human clinical trials was ciluprevir (BILN-2061), whose discovery was predicated on earlier studies that identified 54, a 6 amino acid N-terminal cleavage product of an NS5A/5B substrate, as a competitive inhibitor of NS3 [103,104], Although the development of ciluprevir was halted due to cardiotoxicity in animals, it demonstrated that a potent... 

S ATP -I- peptide <3> (<3> synthetic [9,13,14] <3> e.g. Leu-Glu-Glu-Ser-Ser-Ser-Ser-Asp-His-Ala-Glu-Arg-Pro-Pro-Gly or Arg-Arg-Arg-Glu-Glu-Glu-Glu-Glu-Ser-Ala-Ala-Ala, role of acidic amino acids in peptide substrates, preference for negatively charged amino acids localized to the N-terminal side of a Ser- or Thr-residue, Ser-containing peptides are 4fold better than Thr-containing [9] <3> /1-ARK 1 and 2 prefer peptide substrates with acidic amino acids N-terminal to a Ser-residue [13] <3> /)-ARK 1 prefers peptides containing acidic residues on the N-terminal side of a serine or threonine, presence of activated receptor enhances peptide phosphorylation [14]) (Reversibility <3> [9,13,14]) [9, 13, 14]... 

Subsequently, two cDNA clones encoding barley BEIIa and BEIIb were isolated.263 The major structural difference between the two enzymes was the presence of a 94-amino acid N-terminal extension in the BEIIb precursor. 

C-13 NMR spectrum 1-Dodecanol content Norleucine content C-terminal amino acid N-terminal amino acid Emulsifying activity0... 

Dissolve the dried DNP-amino acid (N-terminal) in 100 pi of acetone. 

Ecotin (eco) is a potent inhibitor of serine proteases that is derived from Escherichia coli. It was originally named for its ability to inhibit trypsin (E. coli trypsin inhibitor), but it is known to interact with and inhibit virtually all characterized tryp-sin-fold serine proteases. It is insensitive to the active site PI preference of the protease (the amino acid N-terminal to the cleaved or scissile bond ) and inhibits proteases with specificity towards basic, large hydrophobic, small aliphatic and acidic amino acids [2]. This remarkable breadth of inhibition classifies eco as a fold-specific inhibitor. It forms a unique tetrameric complex consisting of two protease molecules and two inhibitor molecules (the E2P2 complex), binding in a bi-dentate manner with two surface loop regions known as the primary and secondary sites (3) (Fig. 7.1). Eco itself is a 142 amino acid protein that forms a stable... 

All type 1 copper proteins, with the exception of plastocyanin, possess an 20-amino acid N-terminal signal peptide (Figure 1). These peptides help the proteins translocate... 

Serpins consist of a conserved core of three P-sheets and eight or nine a-helices that act collectively in the inhibitory mechanism. As with the Kazal- and Kunitz-type inhibitors, the mechanism involves a surface exposed loop that is termed the reactive center loop (RCL). The RCL presents a short stretch of polypeptide sequence bearing the Pl-Pl scissile bond. Like other serine protease inhibitor families, the PI residue dominates the thermodynamics that govern the interaction between protease and inhibitor. Exposure of the PI residue to solvent is typically brokered by 15 amino acids N-terminal to the PI residue and 5 residues on the C-terminal prime side of the scissile bond. Evidence for dramatic conformational change in the inhibitory mechanism was first provided by the crystal structure of the cleaved form of ai-antitrypsin (37). In this structure and unlike the native form, the reactive center loop was not solvent exposed but occurred as an additional P-strand within the core of the structure. 

The /3 cells synthesize insulin from a single-chain precursor of 110 amino acids termed preproinsulin. The 24-amino-acid N-terminal signal peptide of preproinsulin is rapidly cleaved in the endoplasmic reticulum to form proinsulin (Figure 60-1). Subsequent processing of proinsulin in the secretory granule removes the connector C peptide, giving rise to mature insulin. 

Despite the great numbers of protease and amylase inhibitors found in biological materials, more recent data indicate there is some homology among the inhibitors Comparison of the complete amino acid sequences of lima bean trypsin inhibitors I and IV shows that the two isolnhibltors differ only in that inhibitor IV contains an eight amino acid N-terminal segment and an additional two Asn residues at the C-terminal end not present in inhibitor I (75) ... 

The mammalian Me cyts bs contain 134 amino-acid residues and show 93-98% sequence similarity. OM cyt bs (146 residues) is larger than Me cyts bs and shares only 68% sequence similarity with bovine Me cyt bs " Both Me cyts bs and OM cyt bs have three domains an N-terminal hydrophilic domain, a medial hydrophobic domain, and a C-terminal hydrophilic domain. In the cytosol, the 100-amino-acid N-terminal domain, which binds the A-type heme, participates in electron-transfer reactions.The heme-binding domains of Me cyt bs and OM cyt bs exhibit very similar protein folds. They have six a-helices and four /3-strands, two of which form a short /3-sheet. The heme is located in a pocket formed by four a-helices and a /3-sheet, with its propionates pointing towards the solvent and the opposite heme edge buried in a hydrophobic pocket. The planes of the heme axial His ligands are in a near-parallel orientation (Figure 10). 

Human defensins are synthesized as 94- to 100-ami no-acid preprodefensins that contain a conserved 19 amino-acid N-terminal signal sequence that targets the peptide to the endoplasmic reticulum. TTiis is followed by an anionic propiece, proposed to balance the cationic charge of the defensin (9). 

Cottingham, I.R., Austin, A., Sidebottom, C. and Slabas, A.R. (1988) Purified enoyl-[acyl-carrier-protein] reductase from rape seed Brassica napus) contains two closely related polypeptides which differ by a six-amino-acid N-terminal extension. Biochim. Biophys. Acta 954, 201-207. 

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