All-rounder Cameron Green took a career-best 5-27 as Australia ripped through South Africa's fragile batting before piling on late runs to seize control of the second Test in Melbourne on Monday.After the visitors were dismissed for 189, an aggressive David Warner, in his 100th Test, was unbeaten on 32 and Marnus Labuschagne was not out on five to steer the hosts to 45-1 at stumps on day one.Usman Khawaja was out for one, caught behind by Kyle Verreynne off Kagiso Rabada.SCORECARD | Proteas v Australia - 2nd Test, Day 1Australia won the first of three Tests by six wickets inside two days on a hostile and green Gabba pitch in Brisbane last week.The wicket at the Melbourne Cricket Ground was less bowler-friendly, but captain Pat Cummins surprisingly chose to field at a venue where toss-winning teams normally bat first.South African skipper Dean Elgar said he was bewildered by the decision, but it proved to be inspired in front of 64 876 fans with the Proteas losing early wickets as they again struggled against the hosts' bowling firepower.After slumping to 67-5, Verreynne and Marco Jansen launched a stirring fightback in a gutsy 112-run stand.But then Green - the second-most expensive buy at the Indian Premier League auction last week - went on a blitz, snapping the partnership when Verreynne got an outside edge on 52 that Steve Smith collected.Two balls later, Jansen was gone, caught by wicketkeeper Alex Carey for 59 off Green before the giant Australian bowled Kagiso Rabada and Lungi Ngidi.Green took 4-8 in the spell with the Proteas losing their last five wickets for 10 runs.Early pressure South Africa started the day nervously, losing Sarel Erwee and Theunis de Bruyn cheaply.They were stunned just before lunch when