Function and solution structure of the Arabidopsis thaliana RALF8 peptide.
Frederick, R.O., Haruta, M., Tonelli, M., Lee, W., Cornilescu, G., Cornilescu, C.C., Sussman, M.R., Markley, J.L.(2019) Protein Sci 28: 1115-1126
- PubMed: 31004454 
- DOI: https://doi.org/10.1002/pro.3628
- Primary Citation of Related Structures:  
6NU4 - PubMed Abstract: 
We report the recombinant preparation from Escherichia coli cells of samples of two closely related, small, secreted cysteine-rich plant peptides: rapid alkalinization factor 1 (RALF1) and rapid alkalinization factor 8 (RALF8). Purified samples of the native sequence of RALF8 exhibited well-resolved nuclear magnetic resonance (NMR) spectra and also biological activity through interaction with a plant receptor kinase, cytoplasmic calcium mobilization, and in vivo root growth suppression. By contrast, RALF1 could only be isolated from inclusion bodies as a construct containing an N-terminal His-tag; its poorly resolved NMR spectrum was indicative of aggregation. We prepared samples of the RALF8 peptide labeled with 15 N and 13 C for NMR analysis and obtained near complete 1 H, 13 C, and 15 N NMR assignments; determined the disulfide pairing of its four cysteine residues; and examined its solution structure. RALF8 is mostly disordered except for the two loops spanned by each of its two disulfide bridges.
Organizational Affiliation: 
National Magnetic Resonance Facility at Madison, University of Wisconsin-Madison, Madison, Wisconsin, 53706.