Aspartic acid polypeptide

Poly-L-lysine and polyglutamic acid Poly-L-aspartic acid Polypeptide-mustard conjugates HPMA... 

The data led to tire cycle shown in figure C2.7.8. Here, only tire active site on tire interior enzyme surface (section C2.6) is depicted, consisting of R groups including aspartic acid, glutamic acid and otliers, represented witli tire shortliand Asp, Glu etc tire subscripts represent tlie positions on tlie polypeptide chain. 

Most aspartic proteases are composed of 323 to 340 amino acid residues, with molecular weights near 35,000. Aspartic protease polypeptides consist of... 

The enormous diversity of protein stmcture and function comes from the many ways in which 20 amino acids can combine into polypeptide chains. Consider how many tetrapeptide chains can be made using Just two amino acids, cysteine and aspartic acid ... 

Considerable amounts of glutamic acid, glycine, and alanine, as well as smaller quantities of aspartic acid, serine, threonine, basic amino acids, leucine, phenylalanine, and cystine have been demonstrated in a total hydrolyzate of the nondiffusible fraction by Boulanger et al. (BIO). Using Deacidite resin, they separated this material into two polypeptide fractions, acid and alkaline, and found that glutamic acid, aspartic acid, leucine, and certain cystine derivatives were the chief constituents of the former, whereas the latter contained considerable amounts of glycine, basic amino acids, and alanine. 

Very recently 13 the three dimensional structure of the CBH II core was fully determined by X-ray diffraction. The polypeptide chain is folded in a-helices and B-strands (a,B-protein with a central B-barrel built up by seven parallel strands. Six of the )3-strands are linked by a-helices. Near the C-terminus of the enzyme is a tunnel with dimensions well suited to take up a single cellulose chain. Two aspartic acid residues (175 and 221) are probably involved in the active center. 

As a sidebar, it should be noted that there is a domain on the fibronectin molecule which binds to the simple peptide RGD (arginine-glycine-aspartic acid) and this has been explored as a means of interfering with the tumor adhesion process using longer, more stable, polypeptide sequences and other analogues or derivatives (Humphries et al. 1987). 

Scheme 50 Synthesis of Polypeptides Incorporating Diazobenzene-Modified Aspartic Acid[92-941...

The specificity pocket of trypsin can accommodate an arginine side chain of a polypeptide substrate or a benzamidine ion, which acts as a competitive inhibitor. Asp = aspartic acid. 

In summary, protein molecules may contain up to nine amino acids that are readily derivatizable at their side chains aspartic acid, glutamic acid, lysine, arginine, cysteine, histidine, tyrosine, methionine, and tryptophan. These nine residues contain eight principal functional groups with sufficient reactivity for modification reactions primary amines, carboxylates, sulfhydryls (or disulfides), thioethers, imidazolyls, gua-nidinyl groups, and phenolic and indolyl rings. All of these side chain functional groups in addition to the N-terminal a-amino and the C-terminal a-carboxylate form the full complement of polypeptide reactivity within proteins (Fig. 12). 

In the life cycle of HIV, its RNA is translated into a polypeptide chain that is composed of several individual proteins including protease, integrase and reverse transcriptase, but in this form these enzymes are not functional. They must be cleaved by viral proteases from the assembled sequence in order for them to become functional. These posttranslational modifications allow the enzymes to facilitate the production of new viruses. The protease itself is made up of two 99-amino-acid monomers, and an aspartic acid residue in the monomer is required for the cleavage. The protease inhibitors inhibit the enzyme protease and consequently interfere with viral replication and maturation by preventing proteases from cleaving proteins into peptides. In humans, these drugs inhibit cleavage of HIV gag and pol polyproteins, which are part of the essential viral structural components, P7, P9, P17 and P24, and... 

Polypeptides, however, are composed of amino acids with side chains that are longer and therefore the area of allowed conformations is reduced when an alanine (Figure 2.12), aspartic acid (Figure 2.13), or a proline (Figure 2.14) is added to the second peptide unit. Finally, the conformational map for a dipeptide of proline-hydroxyproline is dramatically reduced. Rings in the backbone of any polymer reduce the ability of the polymer backbone to adopt numerous conformations and thereby stiffen the structure. 

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