The winter sun feels welcome, but not so the summer sunburn, thanks to proteins on the surface of nerve cells that enable us to sense different temperatures, new research shows.

Scientists have discovered how just a few of these proteins, called ion channels, distinguish perhaps dozens of discrete temperatures from mildly warm to very hot.

Ion channels are pores in cell membranes controlling the flow of charged ions, which turns (nerve cell) neuron signalling on or off -- in this case to inform the body of the temperature the neuron senses, the Journal of Biological Chemistry reported.

Researchers showed that the building blocks, or subunits, of heat-sensitive ion channels can assemble in many different combinations, yielding new types of channels, each capable of detecting a different temperature.

The discovery, in cell cultures, demonstrates for the first time that only four genes, each encoding one subunit type, can generate dozens of different heat-sensitive channels.

"Researchers in the past have assumed that because there are only four genes, there are only four heat-sensitive channels, but now we have shown that there are many more," said Jie Zheng, associate professor of physiology and membrane biology at the University of California Davis School of Medicine, who led the study.

One of the channels they studied, called TRPV1, reacts to hot temperatures -- about 37 degrees Celsius. It is also responsible for the ability to sense spicy foods, such as chili peppers, said a university statement.

A second channel, TRPV3, responds to temperatures of about 26 degrees Celsius. It also senses many food flavours such as those found in rosemary, oregano, vanilla and cinnamon that elicit a warm sensation.