Protein Synthesis

MOLECULAR MIMICRY BY TRANSLATIONAL FACTORS (Protein Synthesis)

The mechanisms by which several of the translational factors act in protein synthesis have been suggested based on detailed structural analyses. Elongation factor Tu was the first factor for which an X-ray crystallographic structure was determined, and was also the first GTP-binding protein whose structure was elucidated. This protein is organized in three structural domains. […]

TRANSLATIONAL ACCURACY (Protein Synthesis)

A. Types of Potential Errors Given the complexity of protein synthesis, there are many steps at which mistakes can occur, and it is remarkable that the error rate is as low as it is. The two principal categories of translational mistakes are missense errors, in which one amino acid is substituted for another or a […]

THE RIBOSOME (Protein Synthesis)

The bacterial ribosome has been the subject of intense study for several decades. Although the general mechanisms of protein synthesis (as outlined earlier) are reasonably well understood, only recently have structures emerged which make a molecular description of ribosome function appear possible. Because of the high degree of functional and sequence conservation between bacterial and […]

INHIBITORS OF PROTEIN SYNTHESIS

Many compounds have been identified which inhibit different steps in protein synthesis, either by mimicking translational substrates, blocking movement within the ri-bosome, or otherwise interfering with essential interactions (Table III). Some of these inhibitors are clinically relevant antibiotics and others have facilitated functional studies of the ribosome as described earlier. For example aminoglycosides such as […]

POST-TRANSLATIONAL MODIFICATIONS (Protein Synthesis)

Many proteins, in order to perform their role in the cell, must be further processed after they are synthesized on the ribosome. These post-translational modifications involve either proteolysis of the polypeptide backbone or chemical derivatization of protein functional groups. TABLE III Inhibitors of Protein Synthesis Antibiotic Activity Chloramphenicol Blocks peptidyl transferase function Erythromycin Blocks translocation […]

MITOCHONDRIAL PROTEIN SYNTHESIS

In addition to the different translational factors and mechanisms used by eukaryotic organisms as described earlier, an organizational difference exists in eukaryotes that contrasts with prokaryotic protein synthesis. In organisms lacking a nucleus, transcription of the genetic message from DNA to RNA occurs in the same location as translation. In fact, bacterial ribosomes typically begin […]

NONRIBOSOMAL PEPTIDE SYNTHESIS

Nonribosomal peptides are a large family of naturally occurring compounds enzymatically synthesized from amino acids without a nucleic acid template. Many of these peptides have useful pharmacological properties. Vancomycin, for example, inhibits bacterial cell wall synthesis. Cyclosporin and precursors of penicillin are also nonribosomal peptides. These compounds are typically secreted by filamentous fungi, although their […]

PROTEIN SYNTHESIS AND THE RNA WORLD

In considering questions of the origins of life, many researchers have speculated that RNA was the earliest form of life, bridging the gap between a prebiotic era and the modern world of protein catalysts and DNA information storage. This suggestion initially came from the discovery of naturally occurring catalytic RNAs such as the Tetrahymena ribozyme […]

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