Valine residues

On complete hydrolysis, a polypeptide gives two alanine, one leucine, one methionine, one phenylalanine, and one valine residue. Partial hydrolysis gives the following fragments Ala-Phe, Leu-Met, Val-Ala, Phe-Leu. It is known that the first amino acid in the sequence is valine and the last one is methionine. What is the complete sequence of amino acids ... 

Sickle cell disease is caused by a mutation that results in the substitution of a valine residue for a glutamate residue in the sixth position of the hemoglobin P-chain. This results from the substitution of a T for an A in the glutamate codon. When (1) DNA from a patient... 

Csaszar, A. G. 1992. Conformers of Gaseous Glycine, J. Am. Chem. Soc. 114,9568-9575. de Dios, A. C., J. G. Pearson, and E. Oldfield. 1993. Chemical Shifts in Proteins An Ab Initio Study of Carbon-13 Nuclear Magnetic Resonance Chemical Shielding in Glycine, Alanine, and Valine Residues, J. Am. Chem. Soc. 115, 9768-9773. 

S)-Isopropylmorpholine-2,5-dione, six-membered depsipeptide, was polymerized by lipase PC and PPL catalysts [112]. High temperature (100°C or 130°C) was required for the polymerization, yielding biodegradable poly(de-psipeptide). During the polymerization, the racemization of the valine residue took place. Demonstrated was PPL-catalyzed ring-opening polymerization of ethylene isopropyl phosphate, five-membered cyclic phosphate [113]. 

Figure 15. a) The active site of WT HIV protease complexed with A-76889, an inhibitor with a bulky P3 residue. Note the relatively spacious S3 pocket made possible by the presence of the small glycine and valine residues, b) The active site of WT FIV protease complexed with TL-3, an inhibitor with a small P3 residue. Note the relatively small constrained S3 pocket due to the presence of the relatively large isoleucine and glutamine residues. 

Valacyclovir, the L-valyl ester of acyclovir, is a prodrug that can be administered orally in herpes zoster infections. Its absorption rate is approx, twice that of acyclovir. During passage through the intestinal wall and liver, the valine residue is cleaved by esterases, generating acyclovir. 

A quite new type of antibiotic and one of the few naturally-occurring boron compounds is boromycin (86). Hydrolytic cleavage of D-valine with the M(7) hydroxides gave caesium and rubidium salts of this antibiotic, and crystal structure analysis established the formula as (XIIT). The rubidium ion is irregularly coordinated by eight oxygen atoms. Experiments with models showed that the cation site would be the natural place for the—NH3+ end of the D-valine residue, and the whole structure raises the possibility that transport of larger alkali metals is related to the N-ends of peptides and proteins. 

Table II. Sensory Analysis of 0-Aminoacyl Sugars and Peptides Composed of Valine Residues...

Furthermore, a cage-type peptide cyclophane bearing D-valine residues in place of L-valine moieties shows a CD band at 244 nm with of —1.1 x 10 in HEPES buffer at 30.0 °C. It becomes apparent that the four pyridinium moieties bound to the chiral o-valine residues are similarly twisted in the same direction, but the twisted direction of bridging components in the host is opposite to that evaluated for the host bearing L-valine residues. A similar asymmetric character... 

The CD band intensity originated from the host (8) is enhanced in the bilayer vesicle ([0] -i-1.5 x 10 deg cm dmol at 247 nm) relative to the corresponding value in the HEPES buffer at 30.0 °C. In addition, no CD spectral change was observed for at least one day at 30.0 °C. This result indicates that the four pyridinium moieties bound to the chiral L-valine residues in 8 assume highly restricted conformations in the bilayer membrane. Thus, the hybrid assembly seems to furnish a chiral guest-binding site different from that provided by 8 alone in aqueous media without the vesicle. 

Cyclodidemnamide (60) is a weakly cytotoxic, heptapeptide from D. molle from the Philippines [90]. Total synthesis of the proposed structure of cyclodidemnamide gave a product with different spectral data to those of the natural product, which is thought to be a stereoisomer [91]. The stereochemistry of one of the two valine residues in cyclodidemnamide was revised from L-valine to D-valine as a result of the total synthesis of both isomers [92] and the configuration was also reassigned as a result of total synthesis [93]. The hexapeptides, comoramides A (61) and B (62), were isolated from D. molle from Mayotte lagoon in the Comoros Islands, while the heptapeptides, mayotamides A (63) and B (64) were isolated from a separate collection of D. molle from the Comoros Islands [94]. 

When HbS is deoxygenated it tends to "crystallize" in red blood cells, which contain 33% by weight hemoglobin. The crystallization (actually gel formation) distorts the cells into a sickle shape and these distorted corpuscles are easily destroyed, leading to anemia. The introduction of the hydrophobic valine residue in Hb S at position 6 near the end of the molecule helps form a new bonding domain by which the hemoglobin tetramers associate to form long semicrystalline microfilamentous arrays. 3 6 s... 

A symmetric pair of hydrogen bonds join the two carbonyl and NH groups of the D-valine residues in the peptide loops. 

Valine. Residues 43, 47, 54, 57, 63, 108, 116, and 118 clear and well defined. Residue 124 uncertain, region of poorly defined chain. 

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