Head-to-Head Coiled Arrangement of the Subunits of the Animal Fatty Acid Synthase

Abstract

The role of the beta-ketoacyl synthase domains in dimerization of the 2505 residue subunits of the multifunctional animal FAS has been evaluated by a combination of crosslinking and characterization of several truncated forms of the protein. Polypeptides containing only the N-terminal 971 residues can form dimers, but polypeptides lacking only the N-terminal 422 residue beta-ketoacyl synthase domain cannot. FAS subunits can be crosslinked with spacer lengths as short as 6 A, via cysteine residues engineered near the N terminus of the full-length polypeptides. The proximity of the N-terminal beta-ketoacyl synthase domains and their essential role in dimerization is consistent with a revised model for the FAS in which a head-to-head arrangement of two coiled subunits facilitates functional interactions between the dimeric beta-ketoacyl synthase and the acyl carrier protein domains of either subunit.

Architecture of Mammalian Fatty Acid Synthase at 4.5 Å Resolution

“…S1D) with their N termini in close proximity; this is in agreement with cross-links between the N termini of companion KS domains via engineered cysteine residues (33). Another important contribution to the dimer interface comes from the ER domain.…”

“…At their top, the KS domains are contacting the lower part of the DH domains, connecting the lower and upper part of the body in the waist region. The spatial arrangement of these domains may explain why the shortest recombinant N-terminal FAS construct with KS activity must, in addition to KS, also enclose MAT and part of the DH domain, which are surrounding KS in the current structure, and why this construct shows dimerization properties similar to those of the full-length FAS (33). The example of KR demonstrates that the oligomerization contacts are not transferred from the isolated bacterial homologs to the mammalian FAS domains as a rule (Table 1): Whereas the E. coli KR (FabG) is tetrameric (25), the two KR domains of mammalian FAS do not interact.…”

Hypothalamic fatty acid metabolism: A housekeeping pathway that regulates food intake

“…The central catalytic enzyme for de novo fatty acid synthesis is fatty acid synthase (FAS; EC 2.3.1.85). Mammalian species have type I FAS, a 250 kDa multifunctional polypeptide that exists as a head-to-head homodimer, post-translationally modified by the addition of a phosphopantitheine group (55,56) (in contrast, plant and prokaryotic species have type II FAS, with the activity generated from separate proteins). In humans, the expression of FAS is ubiquitous but the expression level is highly variable between tissues.…”

Involvement of de novo synthesized palmitate and mitochondrial EGFR in EGF induced mitochondrial fusion of cancer cells

“…52 Detection of FASN homodimer was performed according to a protocol published by others. 59 Briefly, we treated PC3 cells with vehicle alone or EGF (10 ng/ml) in the presence or absence of AEE788 (5 μM) for 15 min and cells were lysed on ice in RIPA buffer followed by centrifugation to remove the cell debris. The cell lysates were mixed with 2× nonreducing sample buffer (lamellae sample buffer [Biorad] without dithiothreitol) at 1:1 ratio and loaded (without boiling) on to the 6% SDS PAGE.…”