XC1028 from Xanthomonas campestris adopts a PilZ domain‐like structure without a c‐di‐GMP switch |
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Authors: | Tso‐Ning Li Ko‐Hsin Chin Jyung‐Hurng Liu Andrew H‐J Wang Shan‐Ho Chou |
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Institution: | 1. Institute of Biochemistry, National Chung‐Hsing University, Taichung, 40227, Taiwan, Republic of China;2. National Chung Hsing University Biotechnology Center, National Chung‐Hsing University, Taichung, Taiwan, Republic of China;3. Core Facility for Protein Crystallography, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China;4. Institute of Biological Chemistry, Academia Sinica, Nankang, Taipei, Taiwan, Republic of China |
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Abstract: | The crystal structure of XC1028 from Xanthomonas campestris has been determined to a resolution of 2.15 Å using the multiple anomalous dispersion approach. It bears significant sequence identity and similarity values of 64.10% and 70.09%, respectively, with PA2960, a protein indispensable for type IV pilus‐mediated twitching motility, after which the PilZ motif was first named. However, both XC1028 and PA2960 lack detectable c‐di‐GMP binding capability. Although XC1028 adopts a structure comprising a five‐stranded β‐barrel core similar to other canonical PilZ domains with robust c‐di‐GMP binding ability, considerable differences are observed in the N‐terminal motif; XC1028 assumes a compact five‐stranded β‐barrel without an extra long N‐terminal motif, whereas other canonical PilZ domains contain a long N‐terminal sequence embedded with an essential “c‐di‐GMP switch” motif. In addition, a β‐strand (β1) in the N‐terminal motif, running in exactly opposite polarity to that of XC1028, is found inserted into the parallel β3/β1′ strands, forming a completely antiparallel β4↓β3↑β1↓β1′↑ sheet in the canonical PilZ domains. Such dramatic structural differences at the N‐terminus may account for the diminished c‐di‐GMP binding capability of XC1028, and suggest that interactions with additional proteins are necessary to bind c‐di‐GMP for type IV fimbriae assembly. Proteins 2009. © 2008 Wiley‐Liss, Inc. |
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Keywords: | PilZ domain Xanthomonas campestris c‐di‐GMP type IV pilus PA2960 |
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