Wireless sensor network(WSN) consists of energy constrained nodes with limited computing and communicating capabilities. Routing is the area where energy of the nodes can be conserved to prolong the lifetime of the WSN network. There exist some routing protocols, out of which clustering protocols has proven energy efficient because network is divided into multiple clusters and the leader of the cluster will supervise thedata routing to the base station/sink after removing redundant data. In this paper we have used hybrid approach for creating the clusters and for forwarding the data to base station. The Cluster Heads(CHs) for first two rounds will be elected by base-station using centralized algorithm and from third round, CHs are selected by the previous cluster heads using distributed algorithm. We introduce a mobile IGN (Integrated Gateway Node) which acts as an interface between CHs and base station. The data transmission from the sensor nodes to the CH will takes place using proactive algorithm and the data transmission between mobile node and base station uses reactive algorithm. Base-station divides the CHs into sectors and assigns mobile node to each sector with the predefined path to relay the data to it. The mobile nodes which is having unlimited energy resources in this architecture is used to conserve energy and prolong life time of the network compared to other routing protocols.