Work

The Ile128Thr polymorphism influences stability and ligand binding properties of the microsomal triglyceride transfer protein

Year: 2006

Type: article

Abstract: The microsomal triglyceride transfer protein (MTTP) is essential for the assembly of VLDLs. We recently observed that a polymorphism in the MTTP promoter (-493G>T), which is in allelic association with an isoleucine-to-theronine substitution at position 128 (Ile128Thr) in the expressed protein, confers an increased risk of coronary heart disease. Two variant proteins comprising amino acids 16-297 of intact MTTP, MTTP(N)-Ile128 and MTTP(N)-Thr128, had similar native secondary structure content, as judged by circular dichroism. However, the thermal stability of MTTP(N)-Thr128 was greatly reduced, and this protein was also more extensively cleaved in limited proteolysis experiments compared with MTTP(N)-Ile128; both of these findings support a less compact fold. On adding LDL, which includes natively folded apolipoprotein B (apoB), decreased stability of the MTTP(N)-Thr128-LDL complex was observed compared with that of the MTTP(N)-Ile128-LDL complex. In a refined model of the N-terminal domain of MTTP, residue 128 is located in a surface-exposed position, in the same region as an identified MTTP binding site in the homologous apoB protein. Thus, the Ile128Thr polymorphism confers reduced structural stability, leading to decreased binding of MTTP to LDL particles. Because the major MTTP binding target on LDL is apoB, the Ile128Thr polymorphism could target the MTTP-apoB interaction.

Source: Journal of Lipid Research

DOI: 10.1194/jlr.m600072-jlr200

Authors: H. Ledmyr, L. Ottosson, M. Sunnerhagen, E. Ehrenborg

Institutions: Karolinska University Hospital, Karolinska Institutet, Linköping University

Language: English

Topic: Lipid metabolism and disorders

Subfield: Cardiology and Cardiovascular Medicine

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,430