Evidence for a C-terminal structural motif in gastrin and its bioactive fragments in membrane mimetic media.
The conformational preferences of human little gastrin, [Nle(15)] gastrin-17, and its short analogues, gastrin-4 and [beta-Ala(1)] gastrin-5, which include the C-terminal tetrapeptide sequence Trp-Met-Asp-Phe-NH(2) crucial for gastrin bioactivity, were determined by NMR spectroscopy in aqueous solutions of zwitterionic dodecylphosphocholine micelles. Backbone HN chemical shift temperature variance, Halpha chemical shift deviations and complex non-sequential NOE patterns pointed to the C-terminal of [Nle(15)] gastrin-17 adopting an ordered conformation. Distance geometry calculations and NOE-restrained molecular dynamics simulations in membrane mimetic solvent boxes of decane and water indicated the C-terminal tetrapeptide sequence of all three peptides adopted a similar, well defined structure, with a general type IV beta-turn observed for all three peptides. The conformation of [Nle(15)] gastrin-17 consisted of two short helices between Leu(5)-Glu(9) and Ala(11)-Trp(14), with the one helix terminating in a type I beta-turn spanning Gly(13)-Asp(16). The experimental evidence and conformational characteristics of the three peptides in micellar media support a membrane-associated mechanism of receptor recognition and activation for the gastrin hormone family and furthermore point to a possible biologically relevant structural motif for gastrin activity.
Stone
Shane R
SR
Department of Chemistry, University of Cape Town, Private Bag, Rondebosch 7701, Cape Town, South Africa.
Mierke
Dale F
DF
Jackson
Graham E
GE
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D040761:Biomimetic Materials / Q000737:chemistry; D005755:Gastrins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D011487:Protein Conformation; D012997:Solvents; D013816:Thermodynamics
D005755:Gastrins; D010446:Peptide Fragments; D012997:Solvents; C037857:gastrin heptadecapeptide, Nle(15)-