At 1531 GMT, the rand traded at 18.2400 against the dollar, 0.55% weaker than its previous close.
"The rand weakened somewhat over today on the expected reshuffle of the cabinet, as markets remain negative on SA's high political risk," said Investec analyst Annabel Bishop in a research note.
Ramaphosa will announce changes to the national executive at 7:00 p.m. (1700 GMT) on Monday, presidential spokesman Vincent Magwenya said over the weekend.
He is also expected to name for the first time an electricity minister, whose appointment comes at a time when households and industries alike are jostling with 6-10 hours of daily power cuts.
On the stock market, the blue-chip index of top 40 companies ended up 0.62% while the broader all-share index closed 0.52% higher.
The market was lifted by local banks which were up over a percentage point, also buoyed by industrial conglomerate Bidvest Group which closed up over 15%.
But the jump in industrial and banking sector was offset by a continuing drop in mining firms, with the index down 2.33% at day's close.
"With higher interest rates and higher inflation... that's been affecting the mining shares negatively", said Wayne McCurrie, portfolio manager with FNB, adding that it could go on for sometime.
In the last year, the local mining index has shaved off almost a fourth of its market value.
The government's benchmark 2030 bond was up, with the yield down 2.5 basis points to 10.115%.
(Reporting by Anait Miridzhanian and Tannur Anders; Editing by Sherry Jacob-Phillips, Bhargav Acharya and Angus MacSwan)
