title: S-peptide as a potent peptidyl linker for protein cross-linking by microbial transglutaminase from Streptomyces mobaraensis.
abstract: We have found that ribonuclease S-peptide can work as a novel peptidyl substrate in protein cross-linking reactions catalyzed by microbial transglutaminase (MTG) from Streptomyces mobaraensis. Enhanced green fluorescent protein tethered to S-peptide at its N-terminus (S-tag-EGFP) appeared to be efficiently cross-linked by MTG. As wild-type EGFP was not susceptible to cross-linking, the S-peptide moiety is likely to be responsible for the cross-linking. A site-directed mutation study assigned Gln15 in the S-peptide sequence as the sole acyl donor. Mass spectrometric analysis showed that two Lys residues (Lys5 and Lys11) in the S-peptide sequence functioned as acyl acceptors. We also succeeded in direct monitoring of the cross-linking process by virtue of fluorescence resonance energy transfer (FRET) between S-tag-EGFP and its blue fluorescent color variant (S-tag-EBFP). The protein cross-linking was tunable by either engineering S-peptide sequence or capping the S-peptide moiety with S-protein, the partner protein of S-peptide for the formation of ribonuclease A. The latter indicates that S-protein can be used as a specific inhibitor of S-peptide-directed protein cross-linking by MTG. The controllable protein cross-linking of S-peptide as a potent substrate of MTG will shed new light on biomolecule conjugation.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Japan.
authors.forename: Noriho
authors.initials: N
authors.lastname: Kamiya
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Suzuki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Takazawa
authors.forename: Shuji
authors.initials: S
authors.lastname: Takeda
authors.forename: Kimitsuna
authors.initials: K
authors.lastname: Watanabe
authors.forename: Teruyuki
authors.initials: T
authors.lastname: Nagamune
mesh_terms: D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D015202:Protein Engineering; D012260:Ribonucleases / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013302:Streptomyces / Q000201:enzymology*; D011503:Transglutaminases / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D010446:Peptide Fragments; C023560:ribonuclease S-peptide; D011503:Transglutaminases; D012260:Ribonucleases