Polypeptide formation

The side chains do not participate in polypeptide formation and are thus free to interact and react with their environment. 

Polypeptide formation (peptide bond) dehydration R-NH2 and HO-R moieties... 

Figure 20.19 Summary of transcription, RNA splicing entry of mRNA into the cytosol and polypeptide formation. The difference in shading is to indicate the change from DNA to RNA. Splicing is just one of the four processes involved in the processing of the primary RNA transcript (Figure 20.20).

Similar evaluations employing an in vitro reticulocyte assay system failed to provide evidence of diminished polypeptide formation (unpub. obser.). Thus, a consistent pattern emerges in these three systems canavanine does not impede protein synthesis, including aberrant, canavanyl proteins. 

The long-chain a-amino acid esters (40), (41), and (42) form bilayers on sonication in water under acidic conditions. Liposomes prepared from (40) and (42) precipitate if the aqueous medium is neutralized by titration with NaOH. Only liposomes made from (41) are stable even in basic solutions, as shown by electron microscopy52). Polypeptide formation in oriented spherical vesicles was confirmed by FT-IR spectroscopy. The liposomal solution of (41) was freeze-dried and the spectrum obtained from the residue was comparable with one of the polycondensed monolayers. The formation of polypeptide vesicles is illustrated in Scheme 4. 

Polypeptide formation involves a repetition of the process involved in peptide synthesis. 

Kleinkauf, H., and H. Dohren, Nonribosomal polypeptide formation on multifunctional proteins. Trends Biochem. Sci. 8 281-283, 1983. 

Most of the mutations in human APC have been found to result in the conversion of CGA (cytosine-guanine-adenine), which codes for arginine, to TGA (thymine-guanine-adenine), which is a stop codon (Polakis, 1997). The stop codons in m A (UAA, UAG, and UGA) act as a signal during translation that halts polypeptide formation at that point. The result is synthesis of a truncated polypeptide. All t)rpes of mRNA contain stop codons however, if a mutation results in the appearance of a stop codon in a new location, then transcription will stop at that new location. 

The number of residues of methylated amino acids in proteins is generally low and runs from one to four residues per molecule protein. Matsuoka (195) has made a comprehensive survey of the methylated lysines and arginines in a large number of proteins (see Ref. 183 for English translation). Methylation of the amino acid residues occurs after polypeptide formation (199). 

The authors next turn to the structure and composition of the ribosome, a molecular machine that coordinates charged tRNAs, mRNA, and proteins, leading to protein synthesis. The fact that the ribosome is now recognized to be a ribozyme, with the RNA components playing the major role in catalysis, is introduced. The experiments that showed the polarities of polypeptide formation and the translation of mRNA are presented next. Then initiation is described, and the roles of a specialized... 

Similar results are obtained on the polycondensation of long chain ct-amino acid esters in monolayers. As shown in fig. 6 for compound (21) the polymer (b) exhibits a lower surface area per molecule compared to the monomer (a). The polypeptide formation in the oriented monomer film is shown in fig. 7. 

Actinomycin, with the strongest inhibitory action, is a specific inhibitor of DNA-dependent RNA synthesis (it inhibits RNA-polymerases and is firmly bound to DNA). Mitomycin also acts at the DNA level. Chloramphenicol and puromycin inhibit protein synthesis at the level of polypeptide formation during interaction between sRNA and mRNA templates. However, two antibiotics (cyclohexamide and pactamycin) stimulated the formation of certain puffs (Clever, 1967). 

Relationship of actinomycin formation to the synthesis of structurally similar polypeptide antibiotics such as etamycin, echinomycin, polymyxin, bacitracin, gramicidin and the relationship of antibiotic polypeptide formation to protein synthesis. 

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