The Los Angeles Business Journal’s index of the 200 largest local public companies closed down for the week ended Jan. 22, largely on investor concerns about President Barack Obama’s proposal to tighter regulate big banks.

The LABJ index dropped 3 percent to 111.77, with decliners outpacing gainers 130 to 48.

Nara Bancorp Inc. fell 22 percent to $8.80 after the Koreatown bank announced that Chief Executive Min Kim, a longtime bank executive, had resigned for personnel reasons.

OSI Systems Inc. dropped 11 percent to $27.77 after a Morgan Keegan analyst downgraded shares of the Hawthorne security and medical scanning equipment maker from “outperform” to “market perform.”

Big 5 Sporting Goods Corp. lost nearly 9 percent to $13.94 after the El Segundo sporting goods retailer narrowed its earnings outlook.

Despite anxiety in the overall banking sector, one of the largest local gainers was Hanmi Financial Corp., which nearly doubled to $2.18 on media reports that an investor was ready to commit a substantial amount of capital to the struggling Koreatown bank. Similarly, Saehan Bancorp, a Koreatown bank operating under a regulatory consent order, soared nearly 900 percent to $1.39 on similar speculation about a prospective capital infusion.

Wilshire Bancorp Inc. jumped more than 18 percent to 49.45 after the Koreatown bank reported a better-than-expected fourth quarter.