The protein, called MUC1, coats the lining of the stomach, presenting a protective barrier against bacterial infection by Helicobacter - known to cause ulcers and cancers in the stomach.
The research builds on other studies showing that people with a shorter version of the gene which produces the MUC1 protein are at a greater risk of gastric disease.
The new findings explain the protective action of MUC1 and why the length of its parent gene is so important.
Scientists in the University's Faculty of Veterinary Science, University of Melbourne worked on the project in partnership with colleagues at the Brisbane-based Mater Medical Research Institute (MMRI).
Associate Professor Phil Sutton, Head of the University's Immunology and Mucosal Pathogens research group, says the MUC1 protein resembles a Christmas tree.
"It is a very long molecule coated with lots of sugars like pine needles." He says it is this length that is critical in the success, or otherwise, of the protein protecting the lining of the stomach from infection by the Helicobacter bacteria.
"When Helicobacter bacteria enter the stomach and are trying to infect, some of them stick to the surface of the stomach, which is lined with the MUC1 protein. What our work suggests is that when the body detects the bacteria sticking onto the MUC1 protein, it chops the protein off."
This process restricts the number of bacteria that can get through and stick to the surface of the stomach. Fewer bacteria sticking to the surface results in less severe disease and therefore an individual's susceptibility to gastric cancer and gastric ulcers is decreased.
Associate Professor Sutton says shorter versions of the MUC1 gene produce shorter MUC1 protein molecules.
"If you take the MUC1 away, or in humans, if you have a short version of it, it's easier for the bacteria to get through and stick to the surface."
Around 2000 new cases of gastric cancer are diagnosed each year in Australia, with 1200 persons a year dying of the disease. Gastric cancer is even more prevalent in parts of Asia, particularly Japan, where it is the top fatal cancer.
Funding for the research project, provided by the National Health and Medical Research Council for three years, finishes this year. Dr Sutton and his team, along with Associate Professor Mike McGuckin (MMRI), have a joint application for more funding under consideration to build on their research.
"We have a theory that MUC1 is preventing access to the surface (of the stomach) but it's not as simple as that. Understanding why MUC1 is such an important molecule in protecting against the infection and the disease might lead to being able to identify people at high risk of developing the disease."