2d27: Difference between revisions

[[Image:2d27.gif|left|200px]]<br /><applet load="2d27" size="350" color="white" frame="true" align="right" spinBox="true"  

Secretion of fully folded extracellular proteins across the outer membrane of Gram-negative bacteria is mainly assisted by the ATP-dependent type II secretion system (T2SS). Depending on species, 12-15 proteins are usually required for the function of T2SS by forming a trans-envelope multiprotein secretion complex. Here we report crystal structures of an essential component of the Xanthomonas campestris T2SS, the 21-kDa N-terminal domain of cytosolic secretion ATPase XpsE (XpsEN), in two conformational states. By mediating interaction between XpsE and the cytoplasmic membrane protein XpsL, XpsEN anchors XpsE to the membrane-associated secretion complex to allow the coupling between ATP utilization and exoprotein secretion. The structure of XpsEN observed in crystal form P4(3)2(1)2 is composed of a 90-residue alpha/beta sandwich core domain capped by a 62-residue N-terminal helical region. The core domain exhibits structural similarity with the NifU-like domain, suggesting that XpsE(N) may be involved in the regulation of XpsE ATPase activity. Surprisingly, although a similar core domain structure was observed in crystal form I4(1)22, the N-terminal 36 residues of the helical region undergo a large structural rearrangement. Deletion analysis indicates that these residues are required for exoprotein secretion by mediating the XpsE/XpsL interaction. Site-directed mutagenesis study further suggests the more compact conformation observed in the P4(3)2(1)2 crystal likely represents the XpsL binding-competent state. Based on these findings, we speculate that XpsE might function in T2SS by cycling between two conformational states. As a closely related protein to XpsE, secretion ATPase PilB may function similarly in the type IV pilus assembly.

2D27 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Xanthomonas_campestris Xanthomonas campestris]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2D27 OCA].  

[[Category: Chan, N L.]]

[[Category: Chang, J L.]]

[[Category: Chien, Y L.]]

[[Category: Hu, N T.]]

[[Category: Huang, C W.]]

[[Category: Shiue, S J.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:54:37 2008''