Mahlon Hoagland
Encyclopedia
Mahlon Bush Hoagland is an American biochemist
who discovered transfer RNA
(tRNA), the translator of the genetic code.
, Massachusetts
, U.S.
in 1921 to Hudson and Anna Hoagland. Hudson was an American physiologist who was known for co-founding the Worcester Foundation for Experimental Biology with Gregory Pincus. He graduated from The Hill School
in 1940 and attended Williams College, and in 1948 received his M.D. from Harvard Medical School
with intentions of becoming a pediatric surgeon. After a bout with tuberculosis, Hoagland was forced to changed career directions and became involved with research.
Hoagland took a research position at Massachusetts General Hospital
in the lab of Paul Zamecnik
, where he researched and detailed the role of transfer RNA
in forming proteins.
From 1953-1967 Hoagland served as an associate professor of microbiology at Harvard Medical School. In 1967, upon leaving Harvard he was appointed professor in the biochemistry department at the Dartmouth Medical School
. In 1970, Hoagland became
scientific director of the Worcester Foundation for Experimental Biology, retiring in 1985 after 15 years in the directorship.
During their experiments with rat liver cells, Hoagland and Zamecnik noticed that in the presence of ATP
, amino acids associate with heat soluble RNA, which was later named transfer RNA
(tRNA). This amino acid and tRNA complex was later called aminoacyl-tRNA
. Hoagland’s major contribution to the laboratory was in his work with amino acid activating enzymes. He discovered that certain enzymes were required to activate amino acids so they could associate with tRNA molecules and eventually be incorporated into new protein molecules. These enzymes were named aminoacyl tRNA synthetase
s. Incidentally, this lab’s discovery of tRNA supported the theory of complementarity (molecular biology)
proposed by Watson and Crick
.
He was awarded the Franklin Medal
in 1976.
Mahlon Hoagland’s other work involved the carcinogenic effects of beryllium
, biosynthesis of coenzyme A
, as well as liver
regeneration and control.
Biochemist
Biochemists are scientists who are trained in biochemistry. Typical biochemists study chemical processes and chemical transformations in living organisms. The prefix of "bio" in "biochemist" can be understood as a fusion of "biological chemist."-Role:...
who discovered transfer RNA
Transfer RNA
Transfer RNA is an adaptor molecule composed of RNA, typically 73 to 93 nucleotides in length, that is used in biology to bridge the three-letter genetic code in messenger RNA with the twenty-letter code of amino acids in proteins. The role of tRNA as an adaptor is best understood by...
(tRNA), the translator of the genetic code.
Early life
Mahlon Bush Hoagland was born in BostonBoston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...
, Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in 1921 to Hudson and Anna Hoagland. Hudson was an American physiologist who was known for co-founding the Worcester Foundation for Experimental Biology with Gregory Pincus. He graduated from The Hill School
The Hill School
The Hill School is a preparatory boarding school for boys and girls located in Pottstown, Pennsylvania, about 35 miles northwest of Philadelphia....
in 1940 and attended Williams College, and in 1948 received his M.D. from Harvard Medical School
Harvard Medical School
Harvard Medical School is the graduate medical school of Harvard University. It is located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts....
with intentions of becoming a pediatric surgeon. After a bout with tuberculosis, Hoagland was forced to changed career directions and became involved with research.
Hoagland took a research position at Massachusetts General Hospital
Massachusetts General Hospital
Massachusetts General Hospital is a teaching hospital and biomedical research facility in the West End neighborhood of Boston, Massachusetts...
in the lab of Paul Zamecnik
Paul Zamecnik
Paul Charles Zamecnik was an American scientist who played a central role in the early history of molecular biology. He was a professor of medicine at Harvard Medical School and a senior scientist at Massachusetts General Hospital. Zamecnik pioneered the in vitro synthesis of proteins and helped...
, where he researched and detailed the role of transfer RNA
Transfer RNA
Transfer RNA is an adaptor molecule composed of RNA, typically 73 to 93 nucleotides in length, that is used in biology to bridge the three-letter genetic code in messenger RNA with the twenty-letter code of amino acids in proteins. The role of tRNA as an adaptor is best understood by...
in forming proteins.
From 1953-1967 Hoagland served as an associate professor of microbiology at Harvard Medical School. In 1967, upon leaving Harvard he was appointed professor in the biochemistry department at the Dartmouth Medical School
Dartmouth Medical School
Dartmouth Medical School is the medical school of Dartmouth College, located in Hanover, New Hampshire, in the United States. The fourth-oldest medical school in the United States, Dartmouth Medical School was founded in 1797 by New England physician Nathan Smith and grew steadily over the course...
. In 1970, Hoagland became
scientific director of the Worcester Foundation for Experimental Biology, retiring in 1985 after 15 years in the directorship.
Work
By the time Hoagland had joined Huntington Laboratories, his colleagues there were well-known for their work in protein synthesis. In the early 1950s Hoagland and his associates were able to show that polypeptide synthesis occurs on ribosomes. They did this by giving a rat injections of radioactive amino acids, waiting for a defined period of time, extracting the liver, and examining sub-cellular fractions for radioactivity. He found that after longer periods of times (hours, days) radioactively labeled proteins were present in all subcellular fractions. However, if they allowed less time to pass, radioactivity was found in only certain particles, which they deemed the sites of proteins synthesis. These particles were named ribosomes.During their experiments with rat liver cells, Hoagland and Zamecnik noticed that in the presence of ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
, amino acids associate with heat soluble RNA, which was later named transfer RNA
Transfer RNA
Transfer RNA is an adaptor molecule composed of RNA, typically 73 to 93 nucleotides in length, that is used in biology to bridge the three-letter genetic code in messenger RNA with the twenty-letter code of amino acids in proteins. The role of tRNA as an adaptor is best understood by...
(tRNA). This amino acid and tRNA complex was later called aminoacyl-tRNA
Aminoacyl-tRNA
Aminoacyl-tRNA is tRNA to which its cognated amino acid is adhered. Its role is to deliver the amino acid to the ribosome where it will be incorporated into the polypeptide chain that is being produced...
. Hoagland’s major contribution to the laboratory was in his work with amino acid activating enzymes. He discovered that certain enzymes were required to activate amino acids so they could associate with tRNA molecules and eventually be incorporated into new protein molecules. These enzymes were named aminoacyl tRNA synthetase
Aminoacyl tRNA synthetase
An aminoacyl tRNA synthetase is an enzyme that catalyzes the esterification of a specific amino acid or its precursor to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA. This is sometimes called "charging" the tRNA with the amino acid...
s. Incidentally, this lab’s discovery of tRNA supported the theory of complementarity (molecular biology)
Complementarity (molecular biology)
In molecular biology, complementarity is a property of double-stranded nucleic acids such as DNA, as well as DNA:RNA duplexes. Each strand is complementary to the other in that the base pairs between them are non-covalently connected via two or three hydrogen bonds...
proposed by Watson and Crick
Watson and Crick
James D. Watson and Francis Crick were the two co-discoverers of the structure of DNA in 1953. They used x-ray diffraction data collected by Rosalind Franklin and proposed the double helix or spiral staircase structure of the DNA molecule...
.
He was awarded the Franklin Medal
Franklin Medal
The Franklin Medal was a science and engineering award presented by the Franklin Institute, of Philadelphia, PA, USA.-Laureates:*1915 - Thomas Alva Edison *1915 - Heike Kamerlingh Onnes *1916 - John J...
in 1976.
Mahlon Hoagland’s other work involved the carcinogenic effects of beryllium
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
, biosynthesis of coenzyme A
Coenzyme A
Coenzyme A is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle. All sequenced genomes encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it as a substrate...
, as well as liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
regeneration and control.
Works
- Hoagland, MB et al. "A soluble ribonucleic acid intermediate in protein synthesis.”Journal of Biological Chemistry. 1958 Mar; 231(1):241-57.
- Hoagland, M.B. Toward the Habit of Truth: A life in Science. New York: Norton, 1990.
- Dodson, Bert, and Mahlon Hoagland. The Way Life Works: The Science Lover's Illustrated Guide to How Life Grows, Develops, Reproduces, and Gets Along. New York: Times Books, 1995.
External links
- Mahlon Hoagland, tRNA Expert, Dies at 87, The New York Times, 1 October 2009
- Professor Mahlon Hoagland - Daily Telegraph obituary