UPDATE 3-U.S. regulators seize a bank to bankers

* Silverton had 1,400 client banks, 400 shareholder banks

* Bank partners seen unaffected by the failure

* Soured commercial real estate loans blamed

* Silverton failure will cost FDIC fund about $1.3 billion (Recasts, adds further details, quote on banking impact)

By John Poirier

WASHINGTON, May 1 (Reuters) - U.S. regulators seized Silverton Bank of Atlanta on Friday, a bank that provided services to other banks and the biggest bank failure so far this year, but officials said the impact would be minimal.

Silverton had about 1,400 client banks in 44 states and provided services that included credit card operations, clearing accounts and trading of loans, including the real estate loans that were its undoing.

The Federal Deposit Insurance Corp said it had created a bridge bank to take over Silverton, saying this would allow its client banks to maintain their relationship with the least amount of disruption.

"This is not going to change the financial make-up of any of the institutions doing business" with Silverton, said Mitchell Glassman, who heads the FDIC's resolutions and receiverships division.

Silverton, with about $4.1 billion in assets and $3.3 billion deposits, was the largest failure since Downey Savings and Loan was seized in November with about $12.8 billion in assets.

The FDIC said the failure is expected to cost its deposit insurance fund about $1.3 billion.

Silverton's seizure was the 30th U.S. bank failure so far in 2009 and was followed by news that the FDIC had closed a 31st institution: Citizens Community Bank of Ridgewood, New Jersey with assets of about $45.1 million.

An FDIC official blamed Silverton's collapse on about $1 billion in soured commercial real estate loans.

"Those loans experienced significant losses due to credit quality deteriorating," Pamela Farwig, associate director of the FDIC's receivership unit, told a conference call with reporters.

As a so-called correspondent bank, Silverton did not take deposits directly from the general public nor did it make loans to consumers. It was owned by about 400 shareholder banks, described by the FDIC as mostly small, community banks.

The FDIC said it will hold a conference call with Silverton's client banks on Saturday.