Co-expression of human agouti-related protein enhances expression and stability of human melanocortin-4 receptor.

•We successfully developed a platform for high-yield production of hMC4R.•Truncation mutants of hMC4R with T4L insertion increase the solubility and stability.•The junction optimization in ICL3 was powerful to increase the hMC4R stability.•Co-expression of human mini-AgRP in sf9 cells enables excellent stability of hMC4R.•Our findings are essential and directly applicable to the structural study of hMC4R.