Journal of Lipid Research, Vol 37, 1609-1615, Copyright © 1996 by Lipid Research, Inc.
Effects of carboxy-terminal truncation on human lecithin:cholesterol acyltransferase activity
OL Francone, L Evangelista and CJ Fielding
Cardiovascular Research Institute, University of California Medical Center, San Francisco 94143, USA.
Mutagenesis was carried out in human lecithin:cholesterol acyltransferase
(LCAT) to generate mutants with stop codons at positions corresponding to
amino acids 315, 341, 359, 375, 388, 394, and 398 of the 416-amino acid
sequence of the mature enzyme protein. Deletion of the 18 terminal amino
acids of the protein was without effect on LCAT phospholipase or
acyltransferase activity, or the stability of the protein to denaturation
at 37 degrees C. Further deletion led to loss of most of the activity,
associated with a 10-fold increase in the rate of denaturation at 37
degrees C. These data indicate that the proline-rich C-terminus of LCAT is
not required for effective enzyme activity. The loss of activity that
accompanied deletion of residues 394-398 suggests a structural role for
these residues, part of a series of predicted beta-sheet sequences in the
C- terminal third of the LCAT primary sequence.