Protein conjugates, synthesis

LIPOPROTEINS. Blood plasma lipoproteins are prominent examples of the class of proteins conjugated with lipid. The plasma lipoproteins function primarily in the transport of lipids to sites of active membrane synthesis. Serum levels of low density lipoproteins (LDLs) are often used as a clinical index of susceptibility to vascular disease. 

FIGURE 25.7 The pathway of palmhate synthesis from acetyl-CoA and malonyl-CoA. Acetyl and malonyl building blocks are introduced as acyl carrier protein conjugates. Decarboxylation drives the /3-ketoacyl-ACP synthase and results in the addition of two-carbon units to the growing chain. Concentrations of free fatty acids are extremely low in most cells, and newly synthesized fatty acids exist primarily as acyl-CoA esters. 

Han, B.N., Stevens, J.F., and Maier, C.S. (2007) Design, synthesis, and application of a hydrazide-func-tionalized isotope-coded affinity tag for the quantification of oxylipid-protein conjugates. Anal. Chem. 79(9), 3342-3354. 

Sherry, A.D., Brown III, R.D., Geraldes, C.F.C., Koeng, S.H., and Kuan, K.-T. (1989) Synthesis and characterization of the gadolinium (3 + ) complex of DOTA-propylamide A model DOTA-protein conjugate. Inorg. Chem. 28, 620-622. 

Tadayoni, B.M., Friden, P.M., Walus, L.R., and Musso, G.F. (1993) Synthesis in vitro kinetics, and in vivo studies on protein conjugates of AZT Evaluation as a transport system to increase brain delivery. Bioconjugate Chem. 4, 139-145. 

For the synthesis of the peptide-protein conjugates, peptides with a readive linker group, ie a maleimido group at the N-terminal amino function, were required. The synthesis of these peptides... 

From a chemical point of view, the El/ubiquitin thiol ester should be competent to donate ubiquitin to a substrate amino group. In fact, aminoacyl-errzyme thiol esters are used in exactly this way in non-ribosomal polypeptide synthesis, a process that was discovered around the same time as ubiquitin-protein conjugation [5]. In spite of the attractive simplicity of this model, however, biochemical reconstitution studies showed that besides El two additional fractions were required to conjugate ubiquitin to a model substrate. They were called ubiquitin carrier protein (E2) and ubiquitin-protein ligase (E3), respectively, since the respective factors seemed to act sequentially [6]. Interestingly, the E2 factor apparently formed a thiol ester with ubiquitin. Based on these results, Hershko and co-workers proposed the ubiquitin conjugation cascade (Figure 5.1). 

II. Synthesis and Immunological Evaluation of Protein Conjugates of Oligosaccharide Components of Bacterial Polysaccharides... 

Scheme 4. Convergent chemical ligation for the chemical synthesis of the transcription factor-related protein conjugate cMyc-Max 13.

In this chapter, some methods for peptide-polymer conjugate synthesis are described and a number of examples are reviewed to illustrate the use of self-assembling peptide sequences to drive nanoscale organization. Conjugation of polymers with proteins or peptides for reasons other than self-assembly, for example, therapeutic protein or peptide PEGylation to prolong in vivo circulation half-lives, are not covered. 

Robbins, J.B., Kubler-Kielb, J., Vinogradov, E., Mocca, C., Pozsgay, V., Shiloach, J., Schneerson, R. Synthesis, characterization, and immunogenicity in mice of Shigella sonnei O-specific oligosaccharide-core-protein conjugates. PNAS 106 (2009) 7974—7978. 

Robey, F. A. and Fields, R. L. (1989) Automated synthesis of bromoacetyl-modi-fied peptides for preparation of synthetic peptide polymers, peptide-protein conjugates and cyclic peptides. Anal. Biochem. 177, 373-377. 

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