MINNEAPOLIS – In order to grow, Best Buy is shrinking.

The largest U.S. specialty electronics retailer for years expanded quickly by opening big-box stores across the country. But shoppers have started using the hulking stores as showrooms where they can test out products before buying them cheaper elsewhere.

To revamp the struggling chain, Best Buy said Thursday it plans to close 50 of its U.S. big box stores, cut 400 corporate jobs and trim $800 million in costs. The company, which has about 1,400 U.S. locations, also plans to open 100 smaller and more profitable Best Buy Mobile stores throughout the country.

There are six Best Buy stores currently operating in Maine, but none of those stores had been notified Thursday as to whether they would be closed, according to Bart Gillespie, general manager of the Best Buy store at the Maine Mall in South Portland.

Gillespie said Best Buy stores are located in South Portland, Topsham, Biddeford, Augusta, Auburn and Bangor.

A satellite Best Buy store, which had opened two years ago inside The College Store, a retail outlet run by Bowdoin College in Brunswick, is no longer in operation.

“The announcement (that 50 stores would be closed nationwide) is not a harbinger of doom. It’s a smart business decision,” Gillespie said. “I can’t imagine that this store would be in jeopardy.”

The Maine Mall Best Buy store is the largest store in Maine, in both sales volume and physical size, Gillespie said. More than 400 people work at the South Portland Best Buy store.

“How do we position the company so we’re where our customers need us to be?” CEO Brian Dunn asked in a call with analysts Thursday. “We’re clearly going to have more doors and less square footage.”

Best Buy is trying to avoid the fate of its rival Circuit City, which liquidated in 2009 after it struggled with the changing electronics landscape. Sales of TVs, digital cameras and videogame consoles — once the bread-and-butter of electronics retailers — have weakened, while sales of lower-margin items such as tablet computers, smartphones and e-readers have increased. The rise in competition from Internet rivals like Amazon.com and discounters like Target also has hurt electronics retailers.

In addition to closing some of its big box stores, Best Buy said it will focus on what sets it apart from its rivals: trained sales staff that can help shoppers get the most out of their tablets, TVs and other electronic devices, including tech support from its “Geek Squad” service and repair unit.

But even as the Best Buy announced its changes Thursday, the Minneapolis-based company also posted a $1.7 billion fiscal fourth quarter loss that’s partly due to restructuring charges. Best Buy’s adjusted results for the quarter topped Wall Street’s expectations, but as investors worried that the restructuring didn’t go far enough, its shares slid nearly 7 percent to close at $24.77 Thursday.