Wal-Mart has finally sounded the vuvuzela on African expansion. After months of speculation about how it would try to capitalize on the continent’s growth, the retailer is offering $4.2 billion to acquire South Africa’s Massmart Holdings. The price could grate on shareholders’ ears. But the deal gives Wal-Mart a local vehicle — and local knowledge — to help it gain access to a market with a profile that should suit it well.

If the deal is accepted by Massmart, Wal-Mart will be paying close to 13 times the Johannesburg-based retailer’s earnings before interest, tax, depreciation and amortization, or Ebitda. For a company that trades at closer to 7 times Ebitda, that’s a big premium, albeit a drop in the bucket against Wal-Mart’s nearly $200 billion market capitalization.

But Wal-Mart will get a foothold in what should be a bright spot in the world’s growth map. South Africa, where Massmart operates 232 stores from Limpopo in the northeast to the Western Cape, is one of the Civets economies (Colombia, Indonesia, Vietnam, Egypt, Turkey and South Africa) widely hailed as the next sizable emerging markets.

The International Monetary Fund estimates sub-Saharan output will grow nearly 6 percent a year from 2011. Capitalizing on that would be a stretch for Wal-Mart from its Bentonville, Ark., headquarters.