Nomura and his colleagues managed completely to disassemble and then reassemble the 30S ribosomal subunit of E. coli, demonstrating that the 22 parts of the subunit (a 16S RNA molecule and 21 different proteins) contained all the information needed to assemble all the parts into a functional whole (4). Later, the Nomura lab achieved the total reconstitution of functional 50S ribosomal subunits of B. stearothermophilus from a mixture of separated components (two RNA molecules and about 30 different proteins) (5). These were landmark experiments on the self-assembly of complex biological structures. Toward the end of his years in Madison, Nomura examined the mechanism by which E. coli matches the rate of synthesis of ribosomal proteins with the rate of synthesis of ribosomal RNA. Much to everyone’s surprise, it turned out that the regulation was at the level of translation: Several of the ribosomal proteins, if present in excess of the number needed to form ribosomes, would bind specifically to the messenger RNAs encoding ribosomal proteins and repress translation of ribosomal protein message (6).
I had the privilege of reading many of Masayasu’s draft manuscripts describing these brilliant experiments. They came to me typed on yellow paper of the sort that was once used for carbon copies. The manuscripts were collages, assembled from small scraps that were taped together. Masayasu would first write and then rearrange his text by cutting and taping. The manuscripts had a wonderful, subtle aroma that I took to be some sort of soap or aftershave that Masayasu used, but I finally discovered that it was the odor of Scotch Magic Mending Tape, which I had never encountered in large quantity until I read his cut-and-tape manuscripts. Whatever the mechanism of their assembly, these draft manuscripts – not unlike ribosomes – ended up so well constructed that you could hardly imagine any way to improve them. Reading Masayasu’s manuscripts was a lesson in recognizing important problems, and the wonderful logic of his writing could evoke in the reader’s mind the transitory delusion that the reader could think (almost) as clearly as Masayasu.
Madison lost something irreplaceable when Nomura moved away. I pointed out at his goodbye party that “Nomura” is an anagram for “Our Man” and promised that we would always think of him as our man in Irvine. At Irvine, Nomura continued to work on ribosomes, but he turned from bacteria to yeast. He continued to be a major force in ribosome research and was active in research until the very end, discovering that the molecular genetics of yeast ribosomes was significantly different from that of bacteria and rejoicing at all the surprises that he encountered.
Nomura was much honored. He was elected to the National Academy of Sciences, the American Academy of Arts and Sciences, the American Academy of Microbiology, the Royal Netherlands Academy of Arts and Sciences, and the Danish Academy of Arts and Sciences. In 2002, he received the Abbott-ASM Lifetime Achievement Award from the American Society for Microbiology.
Masayasu is survived by his wife, Junko, his daughter, Keiko, his son, Toshi, and his grandson, Jack.
- 1. Nomura, M. (2011) Journey of a molecular biologist. Ann. Rev. Biochem. 80, 16 – 40.
- 2. Hosokawa, K., Fujimura, R.K., and Nomura, M. (1966) Reconstitution of functionally active ribosomes from inactive subparticles and proteins. Proc. Natl. Acad. Sci. USA 55, 198 – 204.
- 3. Guthrie, C. and Nomura, M. (1968) Initiation of protein synthesis: a critical test of the 30S subunit model. Nature 219, 232 – 235.
- 4. Traub, P. and Nomura M. (1968) Structure and function of E. coli ribosomes. V. Reconstitution of functionally active 30S ribosomal particles from RNA and proteins. Proc. Natl. Acad. Sci. USA 59, 777 – 784.
- 5. Nomura, M. and Erdmann, V.A. (1970) Reconstitution of 50S ribosomal subunits from dissociated molecular components. Nature 228, 744 – 748.
- 6. Yates, J.L., Arfsten, A.E., and Nomura M. (1980) In vitro expression of Escherichia coli ribosomal protein genes: autogenous inhibition of translation. Proc. Natl. Acad. Sci. USA 77, 1837 – 1841.
Millard Susman (firstname.lastname@example.org) is professor emeritus of genetics at the University of Wisconsin–Madison.