Scent of a sea lamprey

The chemical composition of a pheromone of the sea lamprey (Petromyzon marinus) — a parasitic fish that invaded the Great Lakes of North America in the early 20th century, is reported in the November issue of Nature Chemical Biology. The authors discovered that the pheromone attracts adult sea lampreys to spawning sites. Identifying the pheromone mixture offers an important, environmentally friendly new lead in developing means to control marauding sea lamprey populations.

Sea lampreys are ancient, leech-like fish that survive by attaching to and sucking out the bodily juices from larger fish. Since establishing a presence in the Great Lakes, they have devastated the fishing industry by preying on commercially important fish species. Researchers have searched for small molecules involved in the mating and migratory habits of the sea lamprey, in order to apply these molecules as potential control agents for these parasitic organisms.

After a 15-year hunt, Sorensen, Hoye and coworkers report the identification of a mixture of steroid-like compounds that are secreted by lamprey larvae and attract adult fish to suitable spawning areas. By concentrating thousands of liters of water containing the larvae, the team separated the secreted molecules into different mixtures and tested them for their ability to direct the swimming of adult sea lampreys. The team found that the sea lamprey pheromone is comprised of three molecules and in the right conditions, they serve as a potent signal to direct migrating adult sea lampreys to appropriate spawning sites.

The identification of this class of sea lamprey pheromones uncovers previously unknown chemical structures and also provides new chemical inspiration for ways to manage the ecological problem created by the invading sea lamprey.

How does kinesin know to go forward?

Entropy drives kinesin forward according to a paper in the November issue of Nature Chemical Biology. Kinesin is a protein that walks—one foot after another—along microtubules delivering vesicle cargo around the cell. Although much is known about how kinesin moves, no one knew exactly what made kinesin walk forward instead of backward.

To address this question, Toshio Yanagida and colleagues used a technique called 'optical tweezers', in which microscopic beads are attached to individual kinesin proteins. Light from a laser beam is used to capture the bead in an 'optical trap' and move the bead and protein around. Using this single-molecule technique, the authors looked at the effects of different forces and temperatures on kinesin walking forward and backward (kinesin can be made to walk backwards by pushing on it with the optical tweezers). These results showed that it is entropy that drives kinesin forward, probably because a forward step along the microtubule is a better 'fit' than a backward step.

Besides increasing our understanding of how kinesin marches around cells, the results of Yanagida and coworkers may be more broadly applicable, explaining how other proteins know where to go along the cytoskeleton—the roadways of a cell.

Kinesin twist

In the November issue of Nature Chemical Biology, a paper reports that kinesin rotates microtubules sideways while it moves forward. Kinesin is a protein that walks—one foot after another—along microtubules in order to move vesicles around the inside of cells. Before this report, scientists generally believed that kinesin moved forward without any side-to-side motion.

Cross and colleagues used microscopy to watch kinesin moving along microtubules. They fitted the microtubules with an arm that stuck out to the side to observe if kinesin motion caused any rotation in the microtubules. Surprisingly, they found that microtubules rotated counterclockwise. In addition, they found that this motion was driven by ATP consumption.

This newly found torque force of kinesin suggests that additional protein-protein interactions could be involved as kinesin walks along, and it should stimulate new efforts to understand the molecular details of this process.

Stealing Hepatitis C's raft

Scientists have found a new drug candidate that can be used to stop the liver-damaging Hepatitis C virus (HCV) from multiplying. The research reported in the November issue of Nature Chemical Biology showed that the molecule keeps the virus from hijacking the lipid-making machinery in its host cell, making it harder for the virus to replicate.

RNA-viruses like HIV and HCV are prone to drug resistance. This may be because the drugs target proteins that the virus itself is making. To look for new drug targets and drugs, Hiroshi Sakamoto and colleagues searched a large number of naturally-occurring compounds for their ability to block the replication of the virus. They found one compound, NA255 from a plant fungus that works by blocking the host cell's ability to make certain lipids called sphingolipids. This decreases the availability of specialized lipid structures called rafts that the virus uses as a platform to replicate itself.

Besides increasing our basic knowledge of how HCV replicates itself within host cells, NA255 brings a new strategy to the anti-HCV arsenal by targeting the host cell's machinery.

Mixture of new sulfated steroids functions as a migratory pheromone in the sea lamprey

Peter W Sorensen, Jared M Fine, Vadims Dvornikovs, Christopher S Jeffrey, Feng Shao, Jizhou Wang, Lance A Vrieze, Kari R Anderson and Thomas R Hoye

Published online: 02 October 2005 | doi 10.1038/nchembio739

First paragraph | Full text | PDF Supplementary information

Entropy rectifies the Brownian steps of kinesin

Yuichi Taniguchi, Masayoshi Nishiyama, Yoshiharu Ishii and Toshio Yanagida

Published online: 09 October 2005 | doi 10.1038/nchembio741

Abstract | Full text | PDF | Supplementary information

A torque component in the kinesin-1 power stroke

Junichiro Yajima and Robert A Cross

Published online: 09 October 2005 | doi 10.1038/nchembio740

First paragraph | Full text | PDF | Supplementary information

Host sphingolipid biosynthesis as a target for hepatitis C virus therapy

Hiroshi Sakamoto, Koichi Okamoto, Masahiro Aoki, Hideyuki Kato, Asao Katsume, Atsunori Ohta, Takuo Tsukuda, Nobuo Shimma, Yuko Aoki, Mikio Arisawa, Michinori Kohara and Masayuki Sudoh

Published online: 16 October 2005 | doi 10.1038/nchembio742

First paragraph | Full text | PDF | Supplementary information