Microsomal triglyceride transfer protein large subunit is a protein that in humans is encoded by the MTTP, also known as MTP, gene.[5][6]
MTTP encodes the large subunit of the heterodimeric microsomal triglyceride transfer protein (MTP). Protein disulfide isomerase (PDI) completes the heterodimeric MTP, which has been shown to play a central role in lipoprotein assembly. Mutations in MTTP can cause abetalipoproteinemia.[6]
Apolipoprotein B48 on chylomicra and Apolipoprotein B100 on LDL, IDL, and VLDL are important for MTP binding.[citation needed]
MTP adds triglycerides to nascent chylomicrons in the intestine, and to VLDL in the liver.[7]
Structure
The large subunit of MTP, also known as the alpha subunit, contains an N-terminal half beta barrel, an alpha helix and a C-terminal lipid binding site that lies between two beta pleated sheets. It is a member of the large lipid transfer protein family, like apolipoprotein B (apo B), with which it interacts, but unlike apo B, it is not secreted. The heterodimer is instead retained in the endoplasmic reticulum due to the presence of a C-terminal KDEL motif on the PDI beta subunit.[8]
Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles.[§ 1]
Drugs that inhibit MTTP prevent the assembly of apo B-containing lipoproteins thus inhibiting the synthesis of chylomicrons and VLDL and leading to decrease in plasma levels of LDL-C.
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Gordon DA (1997). "Recent advances in elucidating the role of the microsomal triaglyceride transfer protein in apolipoprotein B lipoprotein assembly". Curr. Opin. Lipidol. 8 (3): 131–7. doi:10.1097/00041433-199706000-00002. PMID9211060.
Sharp D, Ricci B, Kienzle B, et al. (1994). "Human microsomal triaglyceride transfer protein large subunit gene structure". Biochemistry. 33 (31): 9057–61. doi:10.1021/bi00197a005. PMID7545943.
Shoulders CC, Narcisi TM, Read J, et al. (1995). "The abetalipoproteinemia gene is a member of the vitellogenin family and encodes an alpha-helical domain". Nat. Struct. Biol. 1 (5): 285–6. doi:10.1038/nsb0594-285. PMID7664034. S2CID11860468.
Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID8125298.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.