Protein

Abstract

From the Greek proteion, meaning “first in rank” among the material substrates of life, protein was coined in 1838 by the Dutch physician, Gerhardus J Mulder (1802–80) in connection with his investigations into albumin. His belief that he had discovered a chemical molecule with its own distinct properties was soon challenged, however. The work of the German chemist, Justus von Liebig (1803–73) left protein a general term to denote a whole class of substances that shared the same atomic composition but not the same atomic arrangement.Late 19th-century cell theory and genetics ultimately led to a view of protein as the basic genetic material. This was confirmed in 1935 when Wendell Meredith Stanley (1904–71) purified and crystallised the tobacco mosaic virus. But the protein model of genes—an idea that conformed with all the experimental data from the previous half century—was in turn challenged by the research of James Watson and Francis Crick in the 1950s. DNA theory undermined the importance of protein as the carrier of genetic information; genes now came to be seen as controlling the aminoacids that formed proteins.In was in this context that Linus Pauling (1901–94) recharacterised protein by revealing how genes control both the nature and the position of the aminoacids. This work contributed to the development of the central dogma of molecular biology articulated by Francis Crick in 1957: that information can go from a nucleic acid to another nucleic acid, and from a nucleic acid to a protein, but not from a protein to a protein, nor from a protein to a nucleic acid. The reign of protein as the first-ranking basic unit of life seemed to be over.But the fortunes of protein were reversed in the 1980s. Research on transmissible spongiform encephalopathies highlighted abnormalities in the folding of protein chains (prions). The controversial “protein-only” hypothesis of Stanley Prusiner—that in protein-related diseases the replication of protein does not require specific nucleic acids, so that one protein can modify the form of another simply by transmitting its form—has gradually gained acceptance. Many scientists now believe that prion protein is not a virus, and does not contain its own genetic material. Hence, heredity of form, as distinct from genetic heredity, is an increasingly viable concept. Its potential is to shake the very foundations of molecular biology. By no means has protein relinquished its proteion status. From the Greek proteion, meaning “first in rank” among the material substrates of life, protein was coined in 1838 by the Dutch physician, Gerhardus J Mulder (1802–80) in connection with his investigations into albumin. His belief that he had discovered a chemical molecule with its own distinct properties was soon challenged, however. The work of the German chemist, Justus von Liebig (1803–73) left protein a general term to denote a whole class of substances that shared the same atomic composition but not the same atomic arrangement. Late 19th-century cell theory and genetics ultimately led to a view of protein as the basic genetic material. This was confirmed in 1935 when Wendell Meredith Stanley (1904–71) purified and crystallised the tobacco mosaic virus. But the protein model of genes—an idea that conformed with all the experimental data from the previous half century—was in turn challenged by the research of James Watson and Francis Crick in the 1950s. DNA theory undermined the importance of protein as the carrier of genetic information; genes now came to be seen as controlling the aminoacids that formed proteins. In was in this context that Linus Pauling (1901–94) recharacterised protein by revealing how genes control both the nature and the position of the aminoacids. This work contributed to the development of the central dogma of molecular biology articulated by Francis Crick in 1957: that information can go from a nucleic acid to another nucleic acid, and from a nucleic acid to a protein, but not from a protein to a protein, nor from a protein to a nucleic acid. The reign of protein as the first-ranking basic unit of life seemed to be over. But the fortunes of protein were reversed in the 1980s. Research on transmissible spongiform encephalopathies highlighted abnormalities in the folding of protein chains (prions). The controversial “protein-only” hypothesis of Stanley Prusiner—that in protein-related diseases the replication of protein does not require specific nucleic acids, so that one protein can modify the form of another simply by transmitting its form—has gradually gained acceptance. Many scientists now believe that prion protein is not a virus, and does not contain its own genetic material. Hence, heredity of form, as distinct from genetic heredity, is an increasingly viable concept. Its potential is to shake the very foundations of molecular biology. By no means has protein relinquished its proteion status.