* Macquarie to take 35 percent stake in RWE Grid Holding
* Transaction will not affect Net4Gas sale
* RWE to receive cash component as part of the deal (Recasts, adds details, background)
FRANKFURT, Dec 19 (Reuters) - Australian bank Macquarie has bought a stake in Czech gas grids owned by Germany's No.2 utility RWE, adding to its European infrastructure portfolio as it hunts for stable returns.
Infrastructure investors are looking to buy into safer assets that yield guaranteed returns, such as power and gas grids, amid turbulent stock markets and low interest rates.
Macquarie will acquire minority stakes in Czech gas grids from Germany's E.ON, France's GDF Suez and Slovak gas utility SPP, and swap them for a 35 percent stake in RWE Grid Holding, which will bundle some of RWE's Czech gas distribution activities, RWE said in a statement on Wednesday.
Macquarie, a major force in European infrastructure M&A, has already bought RWE's 4,100 kilometre gas network Thyssengas GmbH for an estimated 500 million euros and led a consortium that won the auction for E.ON's Open Grid Europe gas network in May.
RWE, which expects the transaction to close in the first quarter, said it will also receive a cash component as part of the deal but did not give any financial details.
The deal will not include RWE's gas transmission system operator Net4Gas, which the group is trying to sell as part of a 7 billion euro ($9.3 billion) asset disposal programme, a spokeswoman said.
Along with main rival E.ON, RWE needs to prepare itself for a post-nuclear age following Germany's decision to exit nuclear power, forcing it to invest in renewable energy and reduce its 34-billion-euro debt pile after spending billions of euros on takeovers in the last decade.
The group is under intense pressure from rating agencies to speed up its asset sale programme, which amounts to nearly a third of its market value, to rake in cash for new growth areas as well as to protect its credit rating. ($1 = 0.7568 euros) (Additional reporting by Victoria Bryan in Frankfurt and Tom Kaeckenhoff in Duesseldorf; Editing by Louise Heavens)