The man who knows nucleic acid

Har Gobind Khorana is an Indian American bio-chemist who specialized in the study of proteins and nucleic acids. He shared the Nobel Prize in Physiology of Medicine with Robert W. Holley and Marshall W. Nirenberg in 1968 for discoveries that showed how the nucleic acids, which carriers the genetic code of the cell, controls the cell’s protein synthesis.

Har Gobind Khorana was born in Raipur, a village in Punjab, British India (now in Pakistan).

He attended D.A.V. High School in Multan, in West Punjab. Later, he studied in the University of the Punjab at Lahore, India (now in Pakistan), with the assistance of government scholarships, where he obtained a bachelor’s degree in 1943 and a Master degree in Science in 1945.

He obtained his Ph.D. in Organic Chemistry from the University of Liverpool in 1948 on a Government of India Fellowship. The following year, he pursued postdoctoral studies in Switzerland. He also worked for nearly a year on alkaloid chemistry.

He began to research on nucleic acids during a fellowship at the University of Cambridge (1951) under Sir Alexander Todd. He held fellowships and professorships at the Swiss Federal Institute of Technology in Switzerland, at the University of British Columbia (1952–59) in Canada on “nucleic acids and synthesis of many important biomolecules”, and at the University of Wisconsin (1960–70) in the United States. At Wisconsin, “he helped decipher the mechanisms by which RNA codes for the synthesis of proteins” and “began to work on synthesizing functional genes”.

In 1966 Khorana became a citizen of the United States, and in 1971 he joined the faculty of Biology and Chemistry at the Massachusetts Institute of Technology, where he remained until he retired in 2007.

In addition to the Nobel Prize, Khorana received the Albert Lasker Basic Medical Research Award (1968) and the National Medal of Science (1987).

Research

In 1960s Khorana confirmed Nirenberg’s findings that four different types of nucleotides are arranged on the spiral “staircase” of the DNA molecule. Particular segments of DNA molecules are being copied to RNA molecules in a process called transcription.

When the nucleotides are being read off along a strand of RNA, desired amino acids are being produced with the help of a molecule called ribosome, the process is called translation.  These amino acids are the building blocks of proteins. Khorana added details about which serial combinations of nucleotides form which specific amino acids. He also proved that the nucleotide code is always read in groups of three, called codons. Khorana also determined that some of the codons prompt the cell to start or stop the manufacture of proteins which are called the start and stop codon respectively.

He extended long DNA polymers using non-aqueous chemistry and assembled these into the first synthetic gene, using polymerase (is an enzyme that synthesizes long chains of polymers) and ligase (is an enzyme that catalyzes joining of two large molecules) enzymes that link pieces of DNA together, this led to the invention of Polymerized Chain reaction, widely known as PCR.  These custom-designed pieces of artificial genes are widely used in biological sciences for sequencing, cloning and engineering genome of plants and animals.

After the middle of the 1970s, he and his collaborators studied the biochemistry of bacteriorhodopsin and rhodopsin. Bacteriorhodopsin is a membrane protein that converts light energy into chemical energy. Rhodopsin is a light -sensitive receptor protein involved in sensory transduction of the visual system.

He dedicated most of his life towards research, which paves the way for all modern genetics. Apart from research he also loves to educate and to inculcate scientific temper among next generation.

Let’s get some inspiration from this eminent scientist who teach us the way we evolve.

Article by Moumita Mazumdar and M R Raghul