Acts as a calcium sensor involved in the regulatory pathway for the control of intracellular Na(+) and K(+) homeostasis and salt tolerance. Operates in synergy with CIPK24/SOS2 to activate the plasma membrane Na(+)/H(+) antiporter SOS1. May function as positive regulator of salt stress responses. CBL proteins interact with CIPK serine-threonine protein kinases. Binding of a CBL protein to the regulatory NAF domain of a CIPK protein lead to the activation of the kinase in a calcium- dependent manner. MGCSVSKKKKKNAMRPPGYEDPELLASVTPFTVEEVEALYELFKKLSSSIIDDGLIHKEEFQLALFRNRNRRNLFADRIFDVFDVKRNGVIEFGEFVRSLGVFHPSAPVHEKVKFAFKLYDLRQTGFIEREELKEMVVALLHESELVLSEDMIEVMVDKAFVQADRKNDGKIDIDEWKDFVSLNPSLIKNMTLPYLKDINRTFPSFVSSCEEEEMELQNVSS MOP9.8 At5g24270 Protein SALT OVERLY SENSITIVE 3 CNBL4_ARATH 222 SOS3 Calcineurin B-like protein 4 CBL4