The present invention relates to compositions comprising excipients or solubilizing agents for proteins. The invention relates to the discovery that a peptide derived from the N-terminus extension of the T266 isoform of rhBMP-2 has properties that enhance the solubility of proteins. The invention also relates to methods of resolubilizing a protein that has precipitated, by contacting the protein with a peptide comprised of the 17 amino acid extension of the T266 isoform of rhBMP-2. The invention also relates to methods of increasing the solubility of a protein by contacting the protein with a peptide comprised of the 17 amino acid extension of the T266 isoform of rhBMP-2.