Magazine article Science News

Roach Hormone: Clue to Human Ancestry?

Magazine article Science News

Roach Hormone: Clue to Human Ancestry?

Article excerpt

Roach hormone: Clue to human ancestry?

The strongest hormonal evidence yet of a common ancestry for insects and mammals has been provided by a pair of newly identified neuropeptides, isolated from cockroaches. These chemicals, called leucosulfakinins (LSKs), bear a strong similarity both in structure and function to hormones present in mammals, including humans. The strong similarity between the insect and mammalian neuropeptides, says one of the researchers, Ronald Nachman, is "evidence that our [human] hormones have very ancient roots.'

Biochemical similarities between primitive species, like the cockroach, and more recent branchings on the evolutionary tree, like mammals, serve as "molecular clocks'--a means for identifying and tentatively dating the evolutionary divergence of what were once closely related organisms. The high degree of similarity between the LSKs and two hormones present in humans--human gastrin II and cholecystokinin (CCK)-- indicates that these neuropeptides represent one of the slowest ticking of the molecular clocks, according to Nachman, a chemist at the U.S. Department of Agriculture (USDA) Western Regional Research Center in Berkeley, Calif.

Both LSK and LSK-II--amino-acid-chain molecules released by the Madeira cockroach's brain--appear to be hormones. Fifty-five percent of LSK's amino-acid sequence is identical to human gastrin II's, half of LSK-II's matches that in the frog neuropeptide caerulin and greater than 40 percent of LSK-II's amino-acid chain matches that of CCK. These are the highest percentages of structural similarity reported between insect and vertebrate neuropeptides, according to the researchers. Even more convincing, Nachman says, is that both LSK and LSK-II contain sulfate groups--a rare occurrence in hormones of any species. This same rare sulfation is present in the vertebrate neuropeptides they resemble. …

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