Alanine residue

Importantly, both incretins when secreted by the intestine are rapidly degraded by the dipeptidyl peptidase IV (DPPFV), which removed the two amino-terminus histidine-alanine residues, thereby, inactivating the incretins. This enzyme is present at the surface of the epithelial intestinal cells and capillaries in the vicinity of the K and L cells secreting GIP and GLP-1, respectively. It is also present in the... 

FIGURE 4.4. The relaxation of steric interactions by energy minimization. The figure shows the result of an energy minimization of the Gly 12— Ala mutant of BPTT from the native geometry (light) where it has bad steric contacts, to a relaxed geometry (dark). The mutant Alanine residue is drawn as a sphere. 

Examination of the backbone torsion angles in a number of crystal stractures of /9-alanine-containing peptides reveals that the conformation around the C(a)-C(/9) bond of /9-alanine residues is essentially gauche or trans (anti) with values close to 60° or 180°, respectively [158]. Populating the gauche conformation of /9-ami-... 

Fig. 3.8 Variations to solid phase synthesis of polyamides. Use of Fmoc monomers on jS-Ala-Wang resin (left) provides polyamides containing a jS-alanine residue near the C-ter-mini. Polyamides synthesized on the Kaiser...

Fig. 8.1 Biosynthesis of peptidoglycan. The large circles represent A -acetylglucosamine orN-acetylmuramic acid to the latter is linked initially a pentapeptide chain comprising L-alanine, D-glutamic acid and meso-diaminopiraelic acid (small circles) terminating in two D-alanine residues (small, darker circles). The lipid molecule is undecaprenyl phosphate. In the initial (cytoplasm) stage where inhibition by the antibiotic D-cycloserine is shown, two molecules of Dalanine (small circles) are converted by an isomerase to the D-forms (small, darker circles), alter which a ligase joins the two D-alanines together to produce a D-alanyl-D-alanine dipeptide.

The /3-lactam bond is broken (instead of the equivalent peptide bond joining the alanine residues) but the remaining ring system in the /3-lactam (a thiazolidine in penicillins) is not released (Fig. 8.3). Instead, the transpeptidase remains linked to the hydrolysed antibiotic with a half hfe of 10-15 minutes. Whilst bound to the / -lactam, the transpeptidase cannot participate in further rounds of peptidoglycan... 

Fig. 9. The 3/Hn coupling constants versus temperature for different alanine residues in XAO peptide. The reversibility of 3/hn coupling constant versus temperature was checked by measurements with temperature increasing from 2° to 56°C (labeled as heating) or decreasing from 56° to 6°C (labeled as cooling). The errors are the same in heating and cooling measurements the error bars are shown only for heating measurements for clarity. The conditions were temperature from 2° to 56°C, concentration ca. 4 mM, in 30 mM sodium acetate buffer (pH = 4.6, 10% D20 ). From Shi et al. (2002). Proc. Natl. Acad. Sd. USA 99, 9190-9195, 2002 National Academy of Sciences, USA.

We have employed a more systematic random mutagenesis approach by dividing the BDI into consecutive clusters of 10 amino acid residues (Boxes) that are individually replaced with a string of 10 alanine residues in the full-length Hisg-tagged allele to facilitate affinity purification of the mutant protein (Valasek et ah, 2004). Alternatively, clusters rich in... 

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