Protein Sequences from Mastodon and Tyrannosaurus Rex Revealed by Mass Spectrometry : Protein Sequences from Mastodon and Tyrannosaurus Rex Revealed by Mass Spectrometry John M. Asara, Mary H. Schweitzer,Lisa M. Freimark, Matthew Phillips, Lewis C. Cantley. Science. 13 April 2007, 316, 280-285. Derick Lucas
Discovery at Hell Creek Formation : Discovery at Hell Creek Formation Uncovered well-preserved Tyrannosaurus Rex fossils.
Fossils contained femora and medullary bone tissue.
Analysis suggests preservation of collagen α1t1.
Study evolution through known sequences.
Properties of Collagen : Properties of Collagen Peptide triple Helix.
Most abundant peptide in bone.
Large abundance of Glycine and Proline.
Post-translational hydroxylation (modification).
Easily detected.
Durable and resistant to degradation.
Highly conserved.
General Proteomics Method : General Proteomics Method Matched tryptic peptid fragments with sequences from orthologous extant taxa.
Compared sequences of related orthologs to generate protein sequence of likely drifts in amino acids.
Matched theoretical fragmentation patterns with unmatched fragments from original fossil sample.
Evolutionary Divergence : Evolutionary Divergence Collagen α1t1 from extant osterich.
160-600 thousand yr. old mastodon. 68 million yr. old Tyrannosaurus Rex.
Ostrich Validity Experiment : Ostrich Validity Experiment Sequest search suggested collagen match between 1) Chicken, 2) Frog, and 3) Japanese newt.
Assumed divergence of ostrich chicken = chicken frog/newt.
Kept fragments of agreement; used consensus where peptides diverged.
Generated theoretical ostrich peptide.
Increased sequence coverage (33-39%) and found 6 new unique peptide sequences for ostrich collagen.
Ostrich Experiment Cont. : Ostrich Experiment Cont.
Mastodon Experiment : Mastodon Experiment Sequest seach found mastodon collagen to match dog, bovine, human, mouse, and elephant.
Used 1) Human, 2) Dog, and 3) Mouse using the same consensus method. (note: no elephant)
Constructed theoretical peptide.
Increased peptide coverage (32-37%); found 4 sequences unique to mastodon collagen .
Mastodon Experiment Cont. : Mastodon Experiment Cont.
Tyrannosaurus Rex Experiment : Tyrannosaurus Rex Experiment BLAST alignment and similarity search of 5 peptides.
Matches: 1) Chicken (58%), 2) Frog (51%), 3) newt (51%). (note: alligator and crocodile unavailable)
Contamination is improbable.
Unique T-Rex peptide sequence not found.
T-Rex Experiment Cont. : T-Rex Experiment Cont.
Conclusions : Conclusions Proteins over 1 million years old can be sequenced.
Refinement of technology and extraction techniques will provide more peptide information.
MS- and bioinformatics-based approach can obtain unknown protein sequences.
There is a need a more comprehensive sequence database.
References : References Asara, J. M.; Schweitzer, M. H.; Freimark, L. M.; Phillips, M.; Cantley, L. C. Science. 2007, 316, 280-285.
Schweitzer, M. H.; Suo, Z.; Avci, R.; Asara, J. M.; Allen, M. A.; Arce, F. T.; Horner J. R. Science. 2007, 316, 277-280.
Nelson, D. L.; Cox, M. M. Lehninger Principles of Biochemistry , 4th Ed.
“Hell Creek Formation”. Encyclopedia Britannica Online.
“Sequest Searches”. Novatia. .