The complete cDNA sequence of a mitochondrial protein from Chinese hamster ovary cells has been determined. This protein, designated P1, was originally identified in cells resistant to the microtubule inhibitor podophyllotoxin (Gupta, 1981). The mutant cell line contained an alteration of the P1 protein that gave rise to a new, more acidic protein, designated M1 (Gupta et al., 1982). The P1 protein was determined to be microtubule-related based on the cross-resistance pattern of the mutants to other microtubule inhibitors, and corelease with tubulin under conditions which cause microtubule depolymerization (Gupta et al., 1982). Subcellular fractionation studies localized this protein to the matrix of the mitochondria (Gupta and Austin, 1987). Antibodies raised against P1 were used to isolate a cDNA clone from human cells (Jindal et al.,1989). The human cDNA clone was used as a probe to screen for clones of the P1 protein in bacteriophage (lambda)gt10/(lambda)gt11 cDNA libraries prepared from CHO cells. The P1 cDNA encodes a protein of 573 amino acids with a relative molecular mass of 60,983 daltons. The first 26 amino acids meet the requirements of a mitochondrial matrix targeting sequence. The mature protein is 547 residues in length with a relative molecular mass of 57,949 daltons. The deduced amino acid sequence shows 97% identity to the the human P1 protein. More interestingly, the amino acid sequence shows extensive homology (42 to 55% identical residues and an additional 15 to 20% conservative replacements) to the chaperonin class of molecular chaperones. This class of proteins includes the hsp60 protein of yeast, the groEL protein of Escherichia coli, the ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit binding protein of plant chloroplasts, and the 62-65-kDa major antigenic protein of mycobacteria and Coxiella burnetii. The homology of P1 with the above proteins begins after the putative mitochondrial presequence and extends to the c-terminal end. Several regions throughout the protein sequence are highly conserved and are proposed to be functional domains of the protein. Also highly conserved is a Gly-Gly-Met repeating motif at the carboxy-terminus. The function of this sequence is undetermined, as yet. A dendrogram was constructed from the sequence homology data. It suggested that mitochondrial P1 evolved from purple bacteria which is the endosymbiont which gave rise to mitochondria. The chaperonin class of proteins have been shown to assist in the assembly of oligomeric protein structures. It is suggested that the P1 protein may play a similar role in mammalian cells. The high degree of homology between P1 and the 65-kDa mycobacterial antigen also suggests that P1 may be involved in certain autoimmune diseases. / Thesis / Master of Science (MS)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23286 |
| Date | 12 1900 |
| Creators | Picketts, David |
| Contributors | Gupta, R. S., Biochemistry |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.002 seconds