Background:The ␤-amino acid adenylation reaction is important for biosynthesis of natural products. Results: We present the crystal structure and a mutational study of the adenylation enzyme VinN involved in vicenistatin biosynthesis. Conclusion: VinN has a characteristic substrate-binding pocket that selectively accommodates ␤-amino acids. Significance: This study could provide clues for ␤-amino acid specificity prediction and protein engineering of adenylation enzymes.

Macrolactam antibiotics such as incednine and cremimycin possess an aliphatic β-amino acid as a starter unit of their polyketide chain. In the biosynthesis of incednine and cremimycin, unique stand-alone adenylation enzymes IdnL1 and CmiS6 select and activate the proper aliphatic β-amino acid as a starter unit. In this study, we describe the enzymatic characterization and the structural basis of substrate specificity of IdnL1 and CmiS6. Functional analysis revealed that IdnL1 and CmiS6 recognize 3-aminobutanoic acid and 3-aminononanoic acid, respectively. We solved the X-ray crystal structures of IdnL1 and CmiS6 to understand the recognition mechanism of these aliphatic β-amino acids. These structures revealed that IdnL1 and CmiS6 share a common recognition motif that interacts with the β-amino group of the substrates. However, the hydrophobic side-chains of the substrates are accommodated differently in the two enzymes. IdnL1 has a bulky Leu220 located close to the terminal methyl group of 3-aminobutanoate of the trapped acyl-adenylate intermediate to construct a shallow substrate-binding pocket. In contrast, CmiS6 possesses Gly220 at the corresponding position to accommodate 3-aminononanoic acid. This structural observation was supported by a mutational study. Thus, the size of amino acid residue at the 220 position is critical for the selection of an aliphatic β-amino acid substrate in these adenylation enzymes. Proteins 2017; 85:1238-1247. © 2017 Wiley Periodicals, Inc.

Edited by M. J. Romao, Universidade Nova de Lisboa, Portugal

Introduction Distal nail embedding due to hyponychium hypertrophy can be caused by traumatic or surgical avulsion of the nail. As a consequence of these changes, the nail plate is blocked through the deformed tip of the toe. Changes that occur at the tip of the big toe are due to bone growth on the dorsal surface of the distal end of the distal phalanx. This study aimed to present a surgical technique for the treatment of hypertrophy of the tip of the toe and evaluate its effectiveness. Material and methods The surgical technique involved remodeling of the tip of the big toe, with removal of the hypertrophied bone of the distal phalanx. The procedure was assessed by using a questionnaire. Results We included the 108 distal embedded nails. A total of 85% of respondents were satisfied with the procedure. Nearly 80% of patients rated the cosmetic effect as good or very good. Conclusions The technique was an effective treatment and increased the quality of life of those with disorders of nail growth associated with hypertrophy of the tip and hyponychium, with bone overgrowth.