US, German scientists sequence oldest fossil human protein ever

    LOS ANGELES, March 8 (Xinhuanet) -- An international research team reported Tuesday that it has extracted and sequenced protein from a Neanderthal dating to approximately 75,000 years ago.

    It is the oldest fossil human protein ever sequenced. The studyled by scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and Washington University in St.Louis, is published in the latest on-line early edition of Proceedings of the National Academy of Sciences.

    This research opens up an exciting possibility of extracting and sequencing protein from other fossils, including earlier humans, as a means of determining the relationships between extinct and living species, and to better understand the phylogenetic relationships, scientists said.

    "This research opens up the possibility of getting detailed protein information from past human populations, to make inferences about the evolution of human diet and physiology," saidErik Trinkaus, co-author of the paper and a professor at Washington University in St. Louis.

    Trinkaus, an influential scholar of Neandertal, has conducted extensive field work to excavate the fossils from Shanidar Cave, Iraq. It is rare to recover a protein of this age and remarkable to be able to determine the amino acid sequence of this protein, he said.

    Similar to the DNA sequences, protein sequences may be used to provide information on the genetic relationships between extinct and living species. As ancient DNA rarely survives, this new method opens up the possibility of determining these relationshipsin much older fossils which no longer contain DNA.

    The research presents the sequence for the bone protein osteocalcin from a Neanderthal from Shandivar Cave as well as osteocalcin sequences from living primates (humans, chimpanzees, gorillas and orangutans). The team found that the Neanderthal sequence was the same as modern humans.

    The team also found a marked difference in the sequences of Neanderthals, humans, chimpanzees and orangutans from that of gorillas and most other mammals. This sequence difference is at position nine where the amino acid hydroxyproline is replaced by proline.

    The authors suggest that this is a dietary response, as the formation of hydroxyproline requires vitamin C, which is ample in the diets of herbivores like gorillas, but may be absent from the diets of the omnivorous primates such as humans and Neanderthals, orangutans and chimpanzees. Therefore, the ability to form proteins without the presence of vitamin C may have been an advantage to these primates if this nutrient was missing from their diets regularly.

    "We suggest that the absence of hydroxylation of Pro-9 in Pan, Pongo and Homo may reflect response to a selective pressure related to a decline in vitamin C in the diet during omnivorous dietary adaptation, either independently or through the common ancestor of these species," the researchers concluded in their paper.

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