Proteins coding genes

The amount of sample required is quite small as little as 10 mole is typical So many peptides and proteins have been sequenced now that it is impossible to give an accurate count What was Nobel Prize winning work m 1958 is routine today Nor has the story ended Sequencing of nucleic acids has advanced so dramatically that it is possible to clone the gene that codes for a particular protein sequence its DNA and deduce the structure of the protein from the nucleotide sequence of the DNA We 11 have more to say about DNA sequencing m the next chapter... 

Messenger RNA (mRNA) serves to carry the information or message that is encoded in genes to the sites of protein synthesis in the cell, where this information is translated into a polypeptide sequence. Because mRNA molecules are transcribed copies of the protein-coding genetic units that comprise most of DNA, mRNA is said to be the DNA-like RNA. ... 

The DNA in a eukaryotic genome can be divided into different sequence classes. These are unique-sequence, or nonrepetitive, DNA and repetitive-sequence DNA. In the haploid genome, unique-sequence DNA generally includes the single copy genes that code for proteins. The repetitive DNA in the haploid genome includes sequences that vary in copy number from two to as many as 10 copies per cell. 

Estimated number of protein-coding genes ranges from 30,000 to 40,000. 

Recently, a gene coding for a novel pectin methylesterase, has been cloned (19). This gene, pemB, codes for a 433 amino add protein induding a N-terminal sequence of 21 amino adds which presents the characteristics of lipoprotein... 

Al-Shawi R., Ghazal P., Clark J. and Bishop J.O. (1989). Intraspecific evolution of a gene family coding for urinary proteins. J Molec Evol 29, 302-313. 

It has been postulated that Chlamydia may produce a heat shock protein that causes tissue damage through a delayed hypersensitivity reaction. C. trachomatis may also possess DNA evidence of toxin-like genes that code for high-molecular-weight proteins with structures similar to Clostridium difficile cytotoxins, enabling inhibition of immune activation. This may explain the observation of a chronic C. trachomatis infection in subclinical PID. 

This chapter has reviewed the application of ROA to studies of unfolded proteins, an area of much current interest central to fundamental protein science and also to practical problems in areas as diverse as medicine and food science. Because the many discrete structure-sensitive bands present in protein ROA spectra, the technique provides a fresh perspective on the structure and behavior of unfolded proteins, and of unfolded sequences in proteins such as A-gliadin and prions which contain distinct structured and unstructured domains. It also provides new insight into the complexity of order in molten globule and reduced protein states, and of the more mobile sequences in fully folded proteins such as /1-lactoglobulin. With the promise of commercial ROA instruments becoming available in the near future, ROA should find many applications in protein science. Since many gene sequences code for natively unfolded proteins in addition to those coding for proteins with well-defined tertiary folds, both of which are equally accessible to ROA studies, ROA should find wide application in structural proteomics. 

Even the genes that code for proteins are more complex in vertebrates than in bacteria. Most, but not all, are expressed as long RNA molecules that are reduced in size by splicing together the coding segments. This yields a continuous template RNA that is sequentially decoded by protein-synthesizing enzymes. 

Evidence for the first oncogene was found when certain mutants of RSV failed to transform cells at high temperature but did transform cells at low temperature. The mutant virus replicated well at both temperatures. This means that the virus contained a tem-perature-sensitive mutation in a gene that coded for a sarcoma-producing protein, that is, for v-src. 

Sukhdeo, S.C., Sukhdeo, M.V.K., Black, M.B. and Vrijenhoek, R.C. (1997) The evolution of tissue migration in parasitic nematodes (Nematoda Strongylida) inferred from a protein-coding mitochondrial gene. Biological Journal of the Linnean Society 61, 281—298. 

---