First there was the Human Genome Project, which began in 1990 and finally ended 11 years later. Now, scientists believe there is another project afoot — one that is perhaps even more important — known, fittingly, as the human “proteome.”
Researchers from Johns Hopkins University and the Institute of Bioinformatics in Bangalore, India, have published a new study outlining their initial catalog of all the proteins in the human body. Intriguingly, the team uncovered 193 proteins that the genome was never believed to encode, suggesting that even after more than a decade of research, there are still mysteries left to be solved.
Founder and director of the Institute of Bioinformatics, Dr. Akhilesh Pandey, remarked that each protein can be thought of as a book in the library of your body. "The difficulty,” Pandey said in a statement, “is that we don't have a comprehensive catalog that gives us the titles of the available books and where to find them. We think we now have a good first draft of that comprehensive catalog."
To identify the various proteins, the team drew samples from 30 tissues and “cut out” each protein using enzymes as a kind of molecular scissors. These “scissors” broke down each protein into individual peptides, which they could then run through a special machine that names each protein and judges its relative abundance in the body.
Unlike genes, which can be easily accessed in the DNA of each cell, proteins aren’t uniform in all parts of the body. Liver proteins, for example, are secreted into the body and help stop bleeding when it occurs. Other proteins, such as immune system proteins, contribute to killing dangerous antibodies that may lead to illness. Dozens others find themselves in various extremities around the body, each performing a unique function.
As Pandey notes, locating these proteins may actually be more useful than cataloging the entire genome. Genes play a vital role in determining many of the characteristics of an organism, but it’s the proteins — the workhorses of the cell — that eventually get the instructions to build tissues and organs. The combination of these two factors — unspecific location and vital importance — give researchers a complex task in compiling the proteome, Pandey says.
With the team’s current research, it will hopefully be easier for future scientists to do empirical and diagnostic work. "We believe our data will become the gold standard in the field,” Pandey said, “especially because they were all generated using uniform methods and analysis, and state-of-the-art machines."
The new catalog will give scientists easy access to a list of proteins that can be readily indexed, rather than crudely searched for on an individual basis. It’s also particularly helpful because, of the proteins encoded by 17,294 genes, or roughly 84 percent of all of the genes in the human genome thought to encode proteins, 193 proteins came from cells that weren’t supposed to code for them.
"This was the most exciting part of this study, finding further complexities in the genome," said Pandey, conceding also that the human proteome will likely never be finished due to its staggering complexity. A more reasonable goal, he finds, is future scientists building upon the team’s existing work and refining it over time. Ultimately, a clearer picture of the human proteome will emerge — a working catalog that can stand up to scientific rigor but always open to edits.
Source: Kim M, Pinto S, Getnet D, et al. A draft map of the human proteome. Nature. 2014.