Mahlon B. Hoagland

Functional alterations in rat liver polysomes associated with starvation and refeeding.

Abstract Microsomes and ribosomes from the livers of rats starved for one week incorporate amino acids less actively than preparations from the livers of rats that have been starved for the same period and then re-fed for ten or fifteen hours. In both starved and starved-re-fed preparations essentially all of the incorporation is on polysomes. Heavy polysomes from the same region of the sucrose gradient retain incorporation differences similar to those observed with cruder preparations. It is concluded that the difference in activity of the microsomes is at least in part an intrinsic property of the polysome itself.

POLYRIBOSOMES FROM ESCHERICHIA COLI: ENZYMATIC METHOD FOR ISOLATION.

Polyribosomes can be rapidly extracted from Escherichia coli by sequential passage of the cells through solutions of a chelating agent and lysozyme in a centrifugal field. Biosynthesis of protein in whole cells and in a cell-free system occurs almost exclusively in the polyribosomes.

Patterns of albumin and general protein synthesis in rat liver as revealed by gel electrophoresis

Abstract Patterns of protein synthesis in rat liver microsomal fractions have been studied using polyacrylamide gel electrophoresis. In vivo patterns were obtained after injecting rats with 14 C-labelled amino acids, and sacrificing them 20 min later. The livers were fractionated by standard techniques. Synthesis of albumin by the liver microsomes was found to be somewhat reduced relative to other proteins, 18–20 h after partial hepatectomy. In vitro patterns were obtained by incubating subcellular fractions with 14 C-labelled amino acids, GTP and an ATP-generating system, and examining the sonic extract of the incorporation mixture. Extracts from regenerating livers again made less albumin relative to other proteins than did normal extracts. In vivo -like patterns were obtained using the 500 × g , 3000 × g , 15 000 × g supernatants, and microsomes with microsomal supernatant. Integrity of the pattern was lost upon dilution of the microsomal supernatant or when polysomes were used with whole supernatant. The major peak in the patterns co-electrophoresed slightly behind rat serum albumin and was identified as albumin by chemical and immunological means.

Commentary on “Intermediate reactions in protein biosynthesis’ by M.B. Hoagland, P.C. Zamecnik and M.L. Stephenson Biochim. Biophys. Acta 24 (1957) 215–216

I first became aware of the challenge of the problem of protein biosynthesis in 1949 at the Huntington Laboratories at the Massachusetts General Hospital, Boston. Paul Zamecnik and a small group of associates were then pioneering the use of 14C-labeled amino acids to explore protein synthesis in mammalian ceils. They were progressing from in vivo systems to tissue slices and thence to the earliest cell-free preparations. They were at pains to show that incorporation of isotopes into protein represented true peptide bond formation, and they had established that the process was coupled to oxidative energy production. I had just finished medical school after a 2-year bout with tuberculosis and had got a postdoctoral position at the Huntington with the thought of returrfing to medicine in a year or two. I worked on the carcinogenic and other biological effects of the metal beryllium a project that convinced me I wanted to continue to do science and over the next 2 years became increasingly interested in Zamecniks work. He encouraged me to get some in-depth exposure to protein chemistry and to biochemical energetics. I spent a year with Kaj Linderstrom-Lang at the Carlsberg Laboratory in Copenhagen and another year with Fritz Lipmann at the Biochem-