The phrase "function as a gateway" is correct and usable in written English.
You can use it when you need to describe something that acts as an entrance to something else. For example, "The museum functions as a gateway to the city's rich history."
Cigarettes, Keyes said, are often the first thing teenagers experiment with, and can function as a "gateway drug" to alcohol.
Concerns about its function as a gateway drug, and evidence that it can cause mental illness in heavy users, have traditionally been at forefront of public debate.
TTC's students come from throughout Asia, and the College is uniquely positioned to function as a gateway into all of Southeast Asia.
Voltage-gated Na+ channels are integral membrane proteins that function as a gateway for a selective permeation of sodium ions across biological membranes.
Some items are bought as a way to work up to an iconic grail, while others function as a gateway purchase, leading you down the branded path toward a greater good.
It may even function as a gateway device.
In the Netherlands transportation is of special importance because the country functions as a gateway for the traffic of goods between western Europe and the rest of the world.
Diagnostic imaging is often the first step in evaluating patients with back pain and likely functions as a "gateway" to a subsequent cascade of interventions.
That case need not, on Schellenberg's view, lead to a dead end but rather functions as a gateway to important new insights about intellectual tasks and religious possibilities.
A book is, more often than not, an object of human scale with which we form an intimate communion, and that functions as a gateway to expanded knowledge.
