Determination of the Self-Association Residues within a Homomeric and a Heteromeric AAA + Enhancer Binding Protein

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• 作者：Edward Lawton¹ ; ^&dagger ; ; Milija Jovanovic¹ ; ^&dagger ; ; Nicolas Joly² ; Christopher Waite¹ ; Nan Zhang¹ ; Baojun Wang³ ; Patricia Burrows¹ ; Martin Buck¹ ; ^{m.buck@imperial.ac.uk" class="auth_mail}
• 关键词：Abbreviations ; bEBP ; bacterial enhancer binding protein ; RNAP ; RNA polymerase ; BACTH ; bacterial two-hybrid
• 刊名：Journal of Molecular Biology
• 出版年：17 April, 2014
• 年：2014
• 卷：426
• 期：8
• 页码：1692-1710
• 全文大小：2042 K

文摘

The 蟽⁵⁴-dependent transcription in bacteria requires specific activator proteins, bacterial enhancer binding protein (bEBP), members of the AAA + (ATPases Associated with various cellular Activities) protein family. The bEBPs usually form oligomers in order to hydrolyze ATP and make open promoter complexes. The bEBP formed by HrpR and HrpS activates transcription from the 蟽⁵⁴-dependent hrpL promoter responsible for triggering the Type Three Secretion System in Pseudomonas syringae pathovars. Unlike other bEBPs that usually act as homohexamers, HrpR and HrpS operate as a highly co-dependent heterohexameric complex. To understand the organization of the HrpRS complex and the HrpR and HrpS strict co-dependence, we have analyzed the interface between subunits using the random and directed mutagenesis and available crystal structures of several closely related bEBPs. We identified key residues required for the self-association of HrpR (D32, E202 and K235) with HrpS (D32, E200 and K233), showed that the HrpR D32 and HrpS K233 residues form interacting pairs directly involved in an HrpR-HrpS association and that the change in side-chain length at position 233 in HrpS affects self-association and interaction with the HrpR and demonstrated that the HrpS D32, E200 and K233 are not involved in negative regulation imposed by HrpV. We established that the equivalent residues K30, E200 and E234 in a homo-oligomeric bEBP, PspF, are required for the subunit communication and formation of an oligomeric lock that cooperates with the ATP 纬-phosphate sensing PspF residue R227, providing insights into their roles in the heteromeric HrpRS co-complex.