Solution structure of a sweet protein single-chain monellin determined by nuclear magnetic resonance and dynamical simulated annealing calculations

Seok Yong Lee, Jung Hoon Lee, Ho Jin Chang, Joong Myung Cho, Jin Won Jung, Weontae Lee

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)

Abstract

Single-chain monellin (SCM), which is an engineered 94-residue polypeptide, has proven to be as sweet as native two-chain monellin. SCM is more stable than the native monellin for both heat and acidic environments. Data from gel filtration HPLC and NMR indicate that the SCM exists as a monomer in aqueous solution. The solution structure of SCM has been determined by nuclear magnetic resonance (NMR) spectroscopy and dynamical simulated annealing calculations. A stable α-helix spanning residues Phe11- Ile26 and an antiparallel β-sheet formed by residues 2-5, 36-38, 41-47, 54- 64, 69-75, and 83-88 have been identified. The sheet was well defined by backbone-backbone NOEs, and the corresponding β-strands were further confirmed by hydrogen bond networks based on amide hydrogen exchange data. Strands β2 and β3 are connected by a small bulge comprising residues Ile38- Cys41. A total of 993 distance and 56 dihedral angle restraints were used for simulated annealing calculations. The final simulated annealing structures (<SA>(k)) converged well with a root-mean-square deviation (rmsd) between backbone atoms of 0.49 Å for secondary structural regions and 0.70 Å for backbone atoms excluding two loop regions. The average restraint energy- minimized (REM) structure exhibited root-mean-square deviations of 1.19 Å for backbone atoms and 0.85 Å for backbone atoms excluding two loop regions with respect to 20 <SA>(k) structures. The solution structure of SCM revealed that the long α-helix was folded into the concave side of a six-stranded antiparallel β-sheet. The side chains of Tyr63 and Asp66 which are common to all sweet peptides showed an opposite orientation relative to H1 helix, and they were all solvent-exposed. Residues at the proposed dimeric interface in the X-ray structure were observed to be mostly solvent-exposed and demonstrated high degrees of flexibility.

Original languageEnglish
Pages (from-to)2340-2346
Number of pages7
JournalBiochemistry
Volume38
Issue number8
DOIs
Publication statusPublished - 1999 Feb 23

All Science Journal Classification (ASJC) codes

  • Biochemistry

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