Shares of Roku Inc. sank 6.2% in morning trade Wednesday, after Best Buy Co. Inc. and Amazon.com Inc. announced a collaboration to sell smart TVs equipped with Amazon's Fire TV operating system, a Roku rival. The collaboration means TVs made by Best Buy's house brand Insignia will no longer be powered by Roku's operating system, according to a report in The Wall Street Journal. Roku disclosed in its 2017 annual report that Amazon.com had accounted for more than 10% of its Roku player revenue in 2017. Meanwhile, Amazon's stock was up 0.2% in morning trade and Best Buy shares surged 3.5%. Roku's stock was still 44% since it closed at $23.50 on Sept. 28, 2017, its first day of trading, while the S&P 500 has gained 7.8% over the same time.