Capital One Bank’s president, Lynn A. Carter, is stepping down at the end of the year, as the McLean-based institution restructures its senior ranks, according to a recent Securities and Exchange Commission filing.

Capital One offered no explanation for the departure. Carter was unavailable for comment.

“With Lynn’s impending departure, we’re taking the opportunity to restructure . . . to build upon and enhance the bank’s commercial bank and retail strategies,” company spokeswoman Tatiana Stead said in an e-mail.

In September, Michael Slocum, executive vice president of commercial banking at Capital One, will become president of that division. Meanwhile, Jonathan Witter, who oversees the bank’s retail operations, small-business lending and branch distribution, will become head of retail banking.

Slocum and Witter are essentially assuming Carter’s duties. To ensure the transition runs smoothly, Stead said Carter, 54, will stay on in an advisory role through next March.

In an internal memo obtained by Capital Business, chief executive Richard Fairbank told employees that the organizational moves will provide a “more integrated customer experience.”

Streamlining the banking unit has been a tireless effort for Capital One, which rolled up three separate banks in the past six years. The credit card giant entered banking in 2005 with the $5.35 billion purchase of Hibernia, a New Orleans-based bank with 293 locations in Louisiana, Mississippi and Texas.

A year later, Capital One tucked New York’s North Fork Bancorp into its portfolio, a $14.6 billion acquisition that gave the company 353 branches in New York, New Jersey and Connecticut. Just last fall, the McLean institution completed the conversion of 200 plus Chevy Chase Bank locations in the Washington area.

RBC Capital Markets analyst Jason Arnold said Capital One is still defining itself in the banking industry, where, because of its considerable credit card business, it is a bit of an anomaly.

“What is the franchise going to be going forward? Are they going to . . . become commercial bank-like or push more on the card side?” he said. Either option, Arnold said, will face regulatory roadblocks.

“We have completed tremendous work to ensure we have a solid infrastructure from which to continue to grow our banking business,” Fairbank said in the memo. He went on to credit Carter with helping to build the bank’s “infrastructure, bring additional banking talent to the organization and establish our banking business model and service culture as we integrated three banks.”

Carter joined Capital One in 2007 from Bank of America as chief operating officer of the banking unit. A year later she took the helm of the division.