~this page has been created as an assignment for Molecular Biology, an undergraduate course at Davidson College~
Prostaglandin H2 Synthase 1 (PGHS) Orthologs
My Favorite Protein has the following amino acid sequence:
Figure 1. The 600 amino acid sequence of prostaglandin H2 synthase 1. The underlined number is above the corresponding single letter code for the amino acid. The yellow highlight: EGF-like domain (a.a. 32-70). The green H: Histidine Active Site (a.a. 207). The blue Y: Cyclooxygenase Active Site (a.a. 385). The red S: Aspirin Acetylated Serine (a.a. 530). Swiss-Prot protein knowledgebase
Human Ortholog:
Figure 2. The 599 amino acid sequence of homo sapien PGHS. The EGF like domain, the histidine and cyclooxygenase active sites and the apsirin acetylation site are all conserved. The yellow highlight: EGF-like domain (a.a. 31-69). The green H: Histidine Active Site (a.a. 206). The blue Y: Cyclooxygenase Active Site (a.a. 384). The red S: Aspirin Acetylated Serine (a.a. 529). Swiss-Prot protein knowledgebase
In the following figures, the "Query" line refers to the amino acid sequence of the sheep PGHS and the "Sbjct" line refers to the amino acid sequence of the specified organisms. The lines are docked by the amino acid number. The center line displays shared amino acids between the two species, a + marks a changed amino acid that does not have a significant effect, and blank spaces show where the amino acids are different. Percentages of conservation refer to the percent of amino acids of a subject species that are conserved from the sheep species. All figures were retreived from a protein search using the amino acid sequence on Blast.
Query: Ovine (sheep) PGHS (my favorite protein)
Sbjct: C Elegans
Figure 3. Selected portions of the C Elegan amino acid sequence of a haem peroxidase family protein that is 39% conserved. A dual oxidase C elegan protein is 41% conserved.Blast.
Sbjct: E Coli
Neither PGHS nor a similar protein evolved in E Coli.Blast.
Sbjct: Homo Sapiens
Figure 4. Selected portions of the 81% conserved homo sapien PGHS.Blast.
Sbjct: Yeast (S cerevisiae)
Neither PGHS nor a similar protein evolved in yeast.Blast.
Sbjct: Fruit Fly (D melanogaster)
Figure 5. Selected portions of a 41% conserved protein with many isoforms that seems unrelated to PGHS.Blast.
Sbjct: Arabidopsis
Figure 6. Selected portions of a 42% conserved pathogen-responsive alpha dioxygenase.Blast.
Sbjct: Mouse (mus musculus)
Figure 7. Selected portions of a 73% conserved mouse prostaglandin synthase.Blast.
Other Species of Interest
Sbjct:Norway Rat (rattus norvegicus) cyclooxygenase 1
Figure 8. Selected portions of a 82% conserved rat cyclooxygenase 1. Blast.
Sbjct:Brook Trout (Salvelinus fontinalis)
Figure 9. Seleced portions of a 76% conserved trout prostaglandin endoperoxide synthase 1, cyclooxygenase 1.Blast.
Other fish species and conservation percentages: zebra fish (77%), spiny dogfish (75%)Blast.
Sbjct: Cow (Bos taurus)
Figure 10. Selected portions of a 75% conserved prostaglandin synthase 2. Blast.
Nitrosomonas europaea (bacteria)
Figure 11. Selected portions of a 45% conserved cyclooxygenase 2. Blast.
Conservation of PGHS Amino Acid Sequence in Different Species
| Rat | 82% |
| Human | 81% |
| Trout | 76% |
| Rabbit, Cow, Dog, Chicken | 75% |
| Mouse | 73% |
| Bacteria, Arabidopsis, Fruit Fly, C. Elegan | <50% |
| E. Coli, Yeast | no orthologs |
Table 1. Various organisms and the percent of conservation with ovine PGHS listed from greatest conservation to least. Blast
Conclusions
The ovine PGHS amnio acid sequence is highly conserved in rats and humans. In the rat, the cyclooxygenase active site is conserved, which makes sense because it is the rat version of cyclooxygenase 1. Amino acids 73-116 constitute the membrane binding motif which lead hydrophobic molecules traveling from inside the cell to the cyclooxygenase active site (Picot, Loll and Garavito, 1994). This particular group of amino acids is 58% conserved in the rat (25 of 43 a.a. are conserved). More than 5/6 of the proteins make up is the globular catalytic domain so the rats and humans with over 80% conservation have a large portion of the catalytic domain conserved and so have similar functions to the ovine PGHS as an enzyme.
Organisms like the mouse, trout and cow that show about 3/4 conservation have highly conserved EGF like domains, and catalytic domains and so have similar functions.
The organisms with a percentage of conservation of less than 50%, like bacteria and the fruit fly, have a small portion of the catalytic domain and so are not similar in function. A few bacteria species, however, have peroxidase or cyclooxygenase enzymes with conservation of less than 50% which says that although not highly conserved, a similar function is served through another structure. Like in Figure 11, although conservation is only 45%, the cyclooxygenase active site is conserved and so is able to function.
References
NCBI Blast. 2005.< http://www.ncbi.nlm.nih.gov/BLAST/Blast.cgi >. Accessed 8 Mar 2005.
Picot D, Loll PJ, Garavito RM. 1994. The X-ray crystal structure of the membrane protein prostaglandin H2 synthase-1. Nature 367:243-49.
SwissProt Protein Knowledgebase. 2005. < http://us.expasy.org/sprot/ >. Accessed 8 Mar 2005.
email me with any questions! amreid@davidson.edu