The son of South Africa's president has resigned from a company owned by a family accused of wielding undue political influence in the country.
Duduzane Zuma said he was leaving his position in a mining company owned by the controversial Gupta family due to "a sustained political attack".
Both President Jacob Zuma and the Gupta family deny that they influenced the appointment of key ministers.
President Zuma is facing increased pressure to resign.
As well as the controversy over the Gupta family, the Constitutional Court recently said the president had violated the constitution by not paying back public money used to upgrade his private residence in Nkandla.
He survived an attempt to impeach him in parliament.
Mr Zuma resigned from Shiva Uranium, a subsidiary of the Gupta-owned Oakbay Investments.
Two members of the Gupta family - non-executive chairman Atul Gupta and head Varun Gupta - have also resigned with immediate effect from Oakbay, but it remains in the family's hands.
The Guptas moved from India to South Africa in 1993 and have acquired interests in computers, mining and air travel.
Mr Zuma's critics have said his relationship to the Guptas is so close that they describe the two families as the "Zuptas".
The Zumas and the Guptas - the 'Zuptas'
- Bongi Ngema-Zuma, one of the president's wives, used to work for the Gupta-controlled JIC Mining Services as a communications officer.
- Duduzile Zuma, his daughter, was a director at Gupta-owned Sahara Computers.
- Duduzane Zuma, a son, was a director in some Gupta-owned companies.
Last month, Deputy Finance Minister Mcebisi Jonas said a member of the Gupta family had offered him the position of finance minister shortly before the unexplained sacking of Nhlanhla Nene from the post.
Mr Jonas said he rejected the offer, calling it "a mockery of our hard-earned democracy".
Following the recent publicity about the Gupta family, a number of financial institutions, including one of the country's biggest banks, First National Bank (FNB), and Barclays Africa have closed the accounts of Oakbay Investments, local papers report.
In a letter to staff leaked to local media, Oakbay head Nazeem Howa reportedly said: "The closure of our bank accounts has made it virtually impossible to continue to do business in South Africa.
"Without bank accounts we may find ourselves in a position where we are unable to pay you‚ our valued employees."
In a statement about his resignation, Mr Zuma said: "Notwithstanding my efforts to participate meaningfully in the economy, aspersions were cast on me and my family."
The young businessman said he hoped his move would help to "preserve jobs" and "de-politicise" his participation in business.
Analysis: Milton Nkosi, BBC News, Joahnnesburg
Duduzane Zuma's resignation may well be too little too late for his father.
Some would say is it his father who should be resigning from the presidency, and not him.
Even some prominent members of the governing African National Congress (ANC) want President Zuma to step aside.
But the reasons that the banks have cut their ties with the Guptas are entirely different.
Financial institutions realised that the Guptas have become bad for business.
The Gupta brothers have always defended their relationship with the young Zuma as a good example of black economic empowerment.