Mammalian myosin IXb (Myo9b) has been shown to exhibit unique motor properties in that it is a single-headed processive motor and the rate-limiting step in its chemical cycle is ATP hydrolysis. Furthermore, it has been reported to move toward the minus-and the plus-end of actin filaments. To analyze the contribution of the light chain-binding domain to the movement, processivity, and directionality of a single-headed processive myosin, we expressed constructs of Caenorhabditis elegans myosin IX (Myo9) containing either the head (Myo9-head) or the head and the light chain-binding domain (Myo9-head-4IQ). Both constructs supported actin filament gliding and moved toward the plus-end of actin filaments. We identified in the head of class IX myosins a calmodulin-binding site at the N terminus of loop 2 that is unique among the myosin superfamily members. Ca 2؉ /calmodulin negatively regulated ATPase and motility of the Myo9-head. The Myo9-head demonstrated characteristics of a processive motor in that it supported actin filament gliding and pivoting at low motor densities. Quantum dot-labeled Myo9-head moved along actin filaments with a considerable run length and frequently paused without dissociating even in the presence of obstacles. We conclude that class IX myosins are plus-end-directed motors and that even a single head exhibits characteristics of a processive motor.Myosins form a large superfamily of actin-based molecular motors that is composed of at least 35 classes (1). Class IX myosins arose in metazoa after the separation of the fungi (1). Invertebrates contain a single myosin class IX gene with the exception of the Drosophila species that have lost their class IX myosin. Bony fishes contain four myosin IX genes and other vertebrates, including mammalia two genes. The two class IX myosins in mammals, Myo9a 2 and Myo9b, exist in multiple splice variants (2). Myo9a has been shown to play a role in epithelial differentiation and morphology whereas Myo9b regulates the migration of macrophages and possibly other immune cells (3, 4). Class IX myosins share a similar structure with the myosins of the other classes, containing a head region, a calmodulin/light chain-binding domain, and a tail region.Additionally, class IX myosins carry some unique features, including a large N-terminal extension preceding the head domain and a long insertion within the head domain in loop 2. The tail region comprises a C1 zinc-binding domain and a RhoGAP domain. Because of this RhoGAP domain, class IX myosins are involved in signal transduction regulating the dynamics of the actin cytoskeleton (2, 5).Mammalian Myo9b, the only class IX myosin studied so far in vitro, exhibits unique mechano-chemical properties. It has been reported to take multiple successive steps along actin filaments without dissociating, indicating that it is a processive motor (6 -8). This is remarkable because Myo9b is a singleheaded myosin. Other myosins that move processively on actin filaments, such as myosin V, dimeric myosin VI, and myosin VII, are two-...

Human gut symbiont bifidobacteria possess carbohydrate-degrading enzymes that act on the O-linked glycans of intestinal mucins to utilize those carbohydrates as carbon sources. However, our knowledge about mucin type O-glycan degradation by bifidobacteria remains fragmentary, especially regarding how they decompose sulfated glycans, which are abundantly found in mucin sugar-chains. Here, we examined the abilities of several Bifidobacterium strains to degrade a sulfated glycan substrate and identified a 6-sulfo-β-d-N-acetylglucosaminidase, also termed sulfoglycosidase, encoded by bbhII from Bifidobacterium bifidum JCM 7004. A recombinant BbhII protein showed a substrate preference toward 6-sulfated and 3,4-disulfated N-acetylglucosamines over non-sulfated and 3-sulfated N-acetylglucosamines. The purified BbhII directly released 6-sulfated N-acetylglucosamine from porcine gastric mucin and the expression of bbhII was moderately induced in the presence of mucin. This de-capping activity may promote utilization of sulfated glycans of mucin by other bacteria including bifidobacteria, thereby establishing the symbiotic relationship between human and gut microbes.

The mammalian class IX myosin Myo9b can move considerable distances along actin filaments before it dissociates. This is remarkable, because it is single headed and because the ratelimiting step in its ATPase cycle is ATP hydrolysis. Thus, it spends most of its cycling time in the ATP-bound state that has a weak affinity for F-actin in other myosins. It has been speculated that the very extended loop 2 in the Myo9b head domain comprises an additional actin-binding site that prevents it from dissociation in the weak binding states. Here we show that two regions in the loop 2 determine the F-actin concentrations needed to maximally activate the steady-state ATPase activity. Together these two regions regulate the amount capable of binding F-actin and the affinity of the nucleotide-free state. The isolated loop 2 behaved like an entropic spring and bound stoichiometrically and with high affinity to F-actin. Subfragment 1 from skeletal muscle myosin II bound to F-actin simultaneously with the isolated loop 2 of Myo9b and could not displace it. Furthermore, the present results imply also a regulatory role for the tail region. Taken together, the results demonstrate that the extended loop 2 in Myo9b binds F-actin and influences the binding of the conventional stereo-specific actin-binding site.Myosin 9b (Myo9b, myr 5) 2 has been reported to move processively along actin filaments, i.e. upon binding to an actin filament it takes multiple consecutive steps before it dissociates (1-3). This is remarkable, because Myo9b is a single-headed myosin. Other myosins that move processively are two-headed and coordinate movement between the two heads (4, 5). Myo9b is also unique in that ATP hydrolysis is the rate-limiting step in the ATPase cycle (6, 7). This means that Myo9b spends a considerable amount of its cycling time in the ATP-bound state that represents a typically weak actin affinity state. However, Myo9b in the ATP-bound state binds with a relatively high affinity to F-actin (6, 7). Nevertheless, kinetic data do not unequivocally support processive movement.It has been speculated that the exceptionally long insertion at the position of loop 2 in the myosin head tethers Myo9b to F-actin and prevents it from diffusing away. The loop 2 in myosins is a surface loop that has been implicated in the initial weak electrostatic interaction with F-actin. In the processive myosin Va this loop is a little longer and more positively charged than in the non-processive class II myosins. An increase in the net positive charge of loop 2 increased the affinity of myosin Va for F-actin in all nucleotide states, whereas a decrease in its net positive charge reduced the affinity (8). Similar findings were also obtained with naturally occurring splice variants of the non-processive myosin V from Drosophila melanogaster and by modifying the loop 2 in class II myosins (8 -12). The processive run length of myosin Va varied with the affinity for F-actin in the weak binding states (13,14). A higher net positive charge of loop 2 increased the pro...

This study proposes a novel design of a parallel-type Independently Controllable Transmission (ICT). The parallel-type ICT can produce a continuously variable transmission ratio and a required angular output velocity that can be independently manipulated by a controller yet not affected by the angular velocity of the input shaft. The proposed parallel-type ICT is composed of two planetary gear trains and two transmission-connecting members. A prototype was built to investigate its kinematic characteristics and verify application feasibility

Crystalline zinc tin oxide (ZTO; zinc oxide with heavy tin doping of 33 at.%) nanowires were first synthesized using the electrodeposition and heat treatment method based on an anodic aluminum oxide (AAO) membrane, which has an average diameter of about 60 nm. According to the field emission scanning electron microscopy (FE-SEM) results, the synthesized ZTO nanowires are highly ordered and have high wire packing densities. The length of ZTO nanowires is about 4 μm, and the aspect ratio is around 67. ZTO nanowires with a Zn/(Zn + Sn) atomic ratio of 0.67 (approximately 2/3) were observed from an energy dispersive spectrometer (EDS). X-ray diffraction (XRD) and corresponding selected area electron diffraction (SAED) patterns demonstrated that the ZTO nanowire is hexagonal single-crystalline. The study of ultraviolet/visible/near-infrared (UV/Vis/NIR) absorption showed that the ZTO nanowire is a wide-band semiconductor with a band gap energy of 3.7 eV.