Fridays are sweet. Everyone acknowledges that everyone else just wants to go home. :)

Genentech Hall knows how to kick off the weekend; There’s a cart of beer on each floor and a “contest” to see which floor can attract the most employees. They drink and they socialize during Happy Hour every Friday.

That’s all I learned today.

Just kidding.

Today’s Journal Club was lead by Oliver on “G Protein Signaling Events Are Activated at the Leading Edge of Chemotactic Cells” from Cell 95, 81-91 (1998), and the lecture was given by Andrew (Iowa) on small G proteins, specifically Rac, Cdc42 and Rho.

I learned that the PH (pleckstrin homology) domain of a protein is responsible for localizing the protein to the membrane. Domains of proteins are modular and can be fused together to form fued proteins. Fused proteins can have multiple domains, each performing a specific function. For example, a domain of a GEF that is responsible for exchanging GDP for GTP on a small GTPase can be fused with a PH domain. This yields a fused protein that both localizes to the membrane and cataylizes the exchange of GDP for GTP.

GEFs (guanine exchange factors) are proteins that facilitate the exchange of GDP for GTP on a small GTPase. When the GTPase is GTP-bound, it is in its active state. In contrast to GEFs, GAPs are the proteins responsible for turning off small GTPases through the hydrolysis of GTP. A small GTPases’s interaction with a GAP results in a GDP-bound GTPase indicating that the GTPase is in the off state.

Rac, Rho and Cdc42 are “cousin-GTPases,” or so says Andrew. Activation of Rac, a small GTPase, results in lamelipodia formation and causes a cell to expand at the active site. The branching activity of actin fillaments is increased. Activation of Cdc42 leads to filopodia formation, but Andrew says to not worry about Cdc42. Activation of Rho results in the formation of parallel actin structures and causes the cell to contract. In a moving cell, it would be ideal for Rac to be very active on the leading edge and Rho on the trailing edge.

Signaling proteins are like readers, writers and erasers. All of them are part of a process or pathway that results in one or more function of a cell.

Writers need readers according to this how-to-cite-text webpage. In biology, proteins can come in any combination of readers, writers and erasers, or they can exist as just readers, writers or erasers.

It’s the end of iGEM bootcamp week one. This week’s experience lesson(s) are to 1. bring your own lunch, 2. keep anti-sleep stimulants on hand (coffee, candy, pretty pens) and 3. get more sleep.

P.S.: Experience lesson 4. is to take AllerClear before coming to work. The stuff worked! I didn’t sneeze today.