Design, pharmacology, and NMR structure of a minimized cystine knot with agouti-related protein activity.
The agouti-related protein (AGRP) is an endogenous antagonist of the melanocortin receptors MC3R and MC4R found in the hypothalamus and exhibits potent orexigenic activity. The cysteine-rich C-terminal domain of this protein, corresponding to AGRP(87-132), exhibits receptor binding affinity and antagonism equivalent to that of the full-length protein. The NMR structure of this active domain was recently determined and suggested that melanocortin receptor contacts were made primarily by two loops presented by a well-structured cystine knot domain within AGRP(87-132) [McNulty et al. (2001) Biochemistry 40, 15520-15527]. This hypothesis is tested here with NMR structure and activity studies of a 34-residue AGRP analogue designed to contain only the cystine knot domain. The designed miniprotein folds to a homogeneous product, retains the desired cystine knot architecture, functions as an antagonist, and maintains the melanocortin receptor pharmacological profile of AGRP(87-132). The AGRP-like activity of this molecule supports the hypothesis that indeed the cystine knot region possesses the melanocortin receptor contact points. Moreover, this potent AGRP analogue is synthetically accessible, may serve in the development of therapeutics for the treatment of diseases related to energy balance. and may also find use as a new reagent for probing melanocortin receptor structure and function.
Jackson
Pilgrim J
PJ
Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA.
McNulty
Joseph C
JC
Yang
Ying-Kui
YK
Thompson
Darren A
DA
Chai
Biaoxin
B
Gantz
Ira
I
Barsh
Gregory S
GS
Millhauser
Glenn L
GL
D054369:Agouti-Related Protein; D000595:Amino Acid Sequence; D019167:Appetite Stimulants / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D002460:Cell Line; D003553:Cystine / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010446:Peptide Fragments / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin / Q000037:antagonists & inhibitors / Q000378:metabolism; D018000:Receptors, Peptide / Q000037:antagonists & inhibitors / Q000378:metabolism
D054369:Agouti-Related Protein; D019167:Appetite Stimulants; D010446:Peptide Fragments; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin; D018000:Receptors, Peptide; C430443:agouti-related protein (86-132), human; D003553:Cystine