TheBiophysical Society of Japan General IncorporatedAssociation for flagerlar protein export, and its complex structure is composed of about 20 difrerellt proteins. The basa] body contains at least five parts accoTding to their functions/ the rod, LP ring. MS ring, C rjng, and type III protein export apparatus, TheC ring is made ofthe switch cemp]ex proteins FliG, FliM, FliN, whichcontrolscounterclockwise-clockwise(CCW/CW)switchingofthemotor rotation and sits on the cytoplasmic face of the MS

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... ng. To understand the switching mechanisms jn detail, we analyzcd the C ring structures ofCCW-bias and CW-locked mutant moters by etectron cryomicroscopy (cryoEM). The CCW-bias and CW-locked phenotypes arise from single point mutation (V135L) and the deletion of residues 169-171 (APAA) in FliG, respectively. We purified the hook basal bodies from the both strains with fliC and c[pP genedjsrupted, collected cryoEM images, and carried out image ana]ysis. The fitting of the crysta] structure of the switch proteins into the 3D map allowed us to build a partial swich cornplex modeS. We wil[ report the structural change between the CCW and CW forms and the switching mecanisrn of flagcl]ar motor rotatien. Bacteria Eng., Kana2awa Uhiv.) 2sE-o4 7-t']v7x?"metucoastcus6 New foci to cjarify lllyeopinsnta gliding Makoto Miyata (Grad. Sbh. Sci., Osaka City [iniv.) Many species of Alycopiasma, pathogenic bacteria form a membrane protrusion at a ce]1 pole, and glide on host cell surfaces, Although the gliding is t'ast and smooth, the mechanisrn is net related to the conventional rnotor proteins or the known bacterial moti]ity such as flage]la or pi]i. We have studied mainly on the fastest spec{es, dycopiasma mohite, which g]ides up to 4,S micron peT s and 27 pN, and proposed a working mode], "The movements generated by ATP hydro]ysis inside cell transmits to a "leg:' protein through a "crank': protein, resu]ting in the repeated catchjng, pulling, and releasing ofsialic acids fixed on the surfhce (Miyata M. Annu Rev Microbio]. 201O 64: 519-37)," To obtain the better images of this gliding mechanism, we ure now werking on (i) fine and who[e structures of g[idjng machinery, (ii) actual movements of legs in gliding. and "ii} ceup]ing of ATP hydrolysis and leg behaviors. ]ai'aduate Schooi of Slrience, Osaha Uhivemsity,4Department of Biotogicat Sc'iences, University of PI'lr'sconsin-th'twaukee) F]avobacterium iohnsoniae is a Grarn-negative bacterium in the phylum Bacteroidetes, which moves rapidty over surfaces at a speed of 1-3 ptmls, Bacteroidete gliding motility is thought te be different ftom any other motility systems, but the molecular mechanism is unknown. We recently found that SprB adhesin is responsjble for the giiding rnotility of F. johnsoniae. Optical microscopic observation using the fiuorescent ]abeling technigue indicated that SprB adhesin rnele ¢ u]es move along a "right-handed closed he]ical loop track" on the bacterial cell membrane, and this movement causes the cell rotation and translation. SprB adhesin is seereted by the Por secretion system (PorSS), whose gene is widely distributed in the phylum Bacteroidetes. even in nonmotile bacteria such as periodontal pathogen Porphyromonas gingivalis. The secretion substrates are recognized by their C-terminal signal domains composed of about 80 amino acid residues. Varieus proteins, such as chitinase and pathogenie eysteine proteinase, are secreted. Thus disruption of PorSS resulted not on]y jn loss of secretion but also motility. In this symposjum, we show the unjque gliding motility and secretion system in Bacteroides, and discuss their relation. Yoshihiro Fukumori, Azuma Taoka {College Sci. Magrietotactic behavior in bacteria was discovered ever 35 years ago by Richard P, B[akemore (Science, 190, 377-379, 1975), The discovery was based on the fact that certain metile, aquatic bacteria orient and migrate along magnetic field lines when subjected to a magnetic field ofthe erder ofthe geomagnetic field, or greater, Furtherrnore, he reported that the magnetotactic bacteria have unique intracytoplasmic rnembrane vesicles natned as magnetosorne. Magnetosemes comprise a chain of regular-sized bio-mineralized magnetite crystals, each ofwhich is surrounded by a lipid bilayer rnernbrane and organie components. Recently, we found that rnagnetosomes of Mitgneto,y)irillum magnetieum AMB-1 are covered with TPR-protein MarnA oligomers outside a lipid bilayer in near-native environments using atomic force rnicroscopy. Furthermore, most magnetosornes are arranged intirnatety along novel eytoskeletalfilamentscomposedofactin-likeprotein,MamK.Lnterestingly,one extremity of the MamK filaments is tocated at the cel]u]ar pole, Philippe and Wu haye proposed that an MCP-like protein may interact with the MamK fi]aments (J, Mol, Biol., 400, 309-322, 2010). Based on these results, we witt discuss stmctural organization of macromoleeular assemblles, magnetosome, cytoskeleton and flagella in magnetotactic bacteria. 2SE-03 70ftz7-ipt)FopptEgevevaee"tt Structural polymorphism and functional differentiation of actin filaments Taro Q. P. Uyeda[, Nobuhisa Umeki], Saku Kijima2, Yusuke Nishikawa3, Kiyotaka Tokuraku], Akira Nagasakii, Taro Q.P, Noguehi2 (tBiomedical Res. inst., ArsZ 2Mlyakonojo tvlrtl, CbL offech" 3Muroran inst. ofIlrch.) Interaction with specific actin binding protejns (ABPs) is believed to define the funetion of the actin filaments. However, the story may not be that simple, because actin filaments are intrinsieally polymorphic. Moreover, ABPs inducc specific conformational changes ofthe filaments, often in a cooperatlve manner so that ABP-induced conformatienal ehanges that eccurred in the bound actin subunit are propagated to neighbor subunits, presumably leading to cooperative bjnding of that ABP to the filaments, Along this llne, we recently showed that coeperative binding of cofilin and HMM to actin filaments is mutually exclusive, so that when cofilin, HMM and actin filaments are mixed, some filaments bound only cofilin while others bound only HMM. Because cosedimentation assays showed that this does not involve competition for a binding site on actin, HMM and cofilin likely induce specific conformational changes in neighbor actin subunits to differentia"y modulate their affinities for cofilin, HMM and other ABPs. This property of actin filaments might have two bio]ogica] imp[ications, First, binding of a small number of a specifie ABP molecules would initiate a domino effeet to drive the conformation of the filament to one structure and consequent]y one function, amp]ifying and fixing the impact ofbiochemieal sigrial or thermal fluctuation that induced the initial binding. Second, because actin filaments change the structure by stretching, they can function as mechanosensoT to [ocal]y regutate ABPs and the function ef the actin cytoskeleton, Molecular xanthusShaevitz motor driven selfiorganization in Myiococcus (Princeton Universiij." Departments of Physics and From wildebeest herds to bacteria] biofilms and every scale in between, how individuals setfiassemb]e into laTge, spatialty complex groups is a key prob]em in undeTstanding collective behavior, mutticellutarity and development. The coordinated motion ofindividua]s at the ce]]ular ]eve] can drive the formation of higher-scale structure is tissues, organisms and even populations, These phenomena arise statistically as ce]]s modulate their directjon and speed in response to both ]oca] and globa] cues. A fu11 understanding of how colleetive behavior in ce]] populations arises has been diencult to achieve because we currently lack the ability to cross spatial scales and draw connections between sensory input, motor control and group formation. Experiments exarnining the effect of specific mutations on single cell movement and group morphology have identified many important rno]ecular players but Iack the abi]ity to probe the behavier of individua]s within groups or physical aspects of coordination.