Brian Kobilka MED ’81 never talked about the Nobel Prize, said Don Regula MED ’82, Kobilka’s classmate at Yale and current Stanford colleague.

“He has never in his life mentioned the Nobel Prize … ever, which means he’s about as humble as you can get,” Regula said.

But that changed on Wednesday, when a 2 a.m. phone call from Sweden informed Kobilka that he and Robert Lefkowitz, his colleague and former mentor, had won the 2012 Nobel Prize in Chemistry

Kobilka and Lefkowitz were awarded the prize for their work on G protein-coupled receptors (GPCRs), a large family of proteins that plays a crucial role in communication within the body. Kobilka currently serves as the chair of the molecular and cellular physiology department at the Stanford University School of Medicine and has made unprecedented progress in understanding the workings of GPCRs — which could be the key to developing better drugs, since nearly half of all medications involve the receptors.

Kobilka’s main contributions to the field of chemistry include isolating the gene sequence for the beta-adrenergic receptor (BAR), a specific GPCR that he would later use as the foundation for his future research. He also obtained the first 3-D image of a BAR interlocked with its signaling molecule, an accomplishment that the Royal Swedish Academy of Sciences called a “molecular masterpiece, the result of decades of research.”

“I’ve been in touch with other former lab members and everybody has been extremely pleased,” said Mark von Zastrow GRD ’87 MED ’87, who did his postdoctoral research in Kobilka’s lab. “We’re all delighted for Brian and we think he’s an absolutely deserving recipient.”

Kobilka could not be reached for comment.

Three former postdoctoral fellows who worked in his lab said Kobilka was an inspiring and accessible mentor who treated them as colleagues rather than just students. All three said they still stay in frequent touch with Kobilka.

Dan Bernstein, a close friend of Kobilka’s and fellow Stanford faculty member, said that in the early days of his Nobel-Prize-winning work, no one thought Kobilka could succeed in obtaining a crystal structure of a bound GPCR receptor, a breakthrough that would enable further research. Rather than involving postdoctoral fellows in time-consuming research that could jeopardize their careers, Bernstein said, Kobilka waited to incorporate his postdoctoral fellows until his research proved to be more promising.

“He kind of combines this intense, driven character with being somebody who doesn’t seem that way because he’s so modest and self-effacing, which makes him really easy to work with cause he’s about the nicest guy in the world,” von Zastrow said.

Two of Kobilka’s former postdoctoral fellows recalled his fondness for practical jokes and a “great sense of humor” that lie behind his more reserved exterior.

Friends and colleagues said that beyond his work as a scientist, Kobilka values his family. He met his wife, Tong Sun Thian, in biology class while they were both studying at the University of Minnesota-Duluth. Thian, a practicing physician, also spends several days a week doing research in Kobilka’s lab. They have two grown children, Jason and Megan.

Outside of the lab, colleagues say Kobilka enjoys the outdoors, especially long-distance biking. Von Zastrow said that when Kobilka turned 50, he decided to run his first marathon, “just as a challenge for himself.”

Kobilka was named a member of the National Academy of Sciences in 2011.