Structure-function relationships of the liver and muscle isoforms of carnitine palmitoyltransferase I. (May 2001)

• Record Type: Journal Article
• Authors: Zammit, V. A.; Price, N. T.; Fraser, F.; Jackson, V. N.
• Is Part Of: Biochemical Society transactions. Volume 29:Number 2(2001)
• Page Start: 287
• Page End: 291
• Publication Date: 2001-05
• Subjects: carnitine palmitoyltransferase -- chimaeric proteins -- malonyl-CoA -- mitochondria -- topology; ACBP, acyl-CoA-binding protein -- CPT, carnitine palmitoyltransferase -- etomoxir, 2-[6-(4-chlorophenoxy) hexyl]oxirane carboxylic acid -- L, liver -- M, muscle -- TM, transmembrane; Biochemistry -- Congresses; 572
• DOI: 10.1042/bst0290287
• Languages: English
• ISSNs: 0300-5127

Abstract

Abstract : Elucidation of the membrane topology of carnitine palmitoyltransferase (CPT) I showed that the extreme N-terminus is involved in determining the sensitivity of the liver (L) isoform to malonyl-CoA and suggested that interaction between the two cytosolic segments of the CPT I molecule determines the kinetic characteristics of the enzyme. Work with chimaeric liver/muscle-isoform (L/M) proteins constructed from all six possible combinations of three domains [N-terminus plus transmembrane domain 1 (TM1), loop plus TM2 and C-domain] expressed in Pichia pastoris showed that the precise N-C and TM1-TM2 pairings determine the overall kinetic parameters of the protein. Discrete short sequences within the respective N-terminal regions have negative or positive effects on malonyl-CoA sensitivity (L-isoform) or the K m for carnitine (M-isoform) in the full-length proteins, thus imparting to them their distinctive kinetic characteristics. Interactions within N-terminal domains also seem to be important in the targeting of the protein to microsomes in the P. pastoris expression system.