LONDON, June 15 (Reuters) - The World Bank's private sector arm has closed a $509-million deal that packages loans extended to developing economies into rated instruments, its second such push to attract more institutional investors.

In a statement published on Monday, the World Bank said the International Finance Corporation initiative was designed to attract private capital at scale for investments in productive sectors with the greatest potential to create jobs and drive growth.

Multilateral development banks are stepping up efforts to mobilise private capital as rising financing needs in emerging markets outstrip traditional lending capacity, while many rich nations are pivoting resources away from development finance.

Here are more details:

• The total consists of a $320 million and $50 million senior tranches sold to private investors, rated Aaa and Aa1 by Moody's respectively, a $80-million mezzanine tranche insured by a consortium of credit insurers and a $59-million equity tranche held jointly by IFC and the UK government.

• The transaction packaged 62 IFC-originated loans across a number of sectors and geographies.

• The June transaction is the second one of its sort after the IFC launched its inaugural collateralised loan obligation of just over $500 million in September.

• "We are finding the challenge is not a lack of capital, it's creating investment products that meet investor needs," said Kevin Njiraini, Director of Syndicated Loans & Mobilization at the IFC.

• The transaction was oversubscribed, said Njiraini, and attracting investors from the U.S., from Europe and - for the first time - from Asia.

• A broader set of investors meant this transaction could be replicated and scaled, he said, adding the IFC's goal was to have more than one or two transactions a year.

• The senior notes are listed on the London Stock Exchange.